825 lines
31 KiB
C++
825 lines
31 KiB
C++
// * jquant1.c
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// *
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// * Copyright (C) 1991-1995, Thomas G. Lane.
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// * This file is part of the Independent JPEG Group's software.
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// * For conditions of distribution and use, see the accompanying README file.
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// *
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// * This file contains 1-pass color quantization (color mapping) routines.
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// * These routines provide mapping to a fixed color map using equally spaced
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// * color values. Optional Floyd-Steinberg or ordered dithering is available.
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#ifdef _MSC_VER
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#pragma warning(push)
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#pragma warning(disable: 4127 4244)
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#endif
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#define JPEG_INTERNALS
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#include "JINCLUDE.h"
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#include "JPEGLIB.h"
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#ifdef QUANT_1PASS_SUPPORTED
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// * The main purpose of 1-pass quantization is to provide a fast, if not very
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// * high quality, colormapped output capability. A 2-pass quantizer usually
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// * gives better visual quality; however, for quantized grayscale output this
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// * quantizer is perfectly adequate. Dithering is highly recommended with this
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// * quantizer, though you can turn it off if you really want to.
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// *
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// * In 1-pass quantization the colormap must be chosen in advance of seeing the
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// * image. We use a map consisting of all combinations of Ncolors[i] color
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// * values for the i'th component. The Ncolors[] values are chosen so that
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// * their product, the total number of colors, is no more than that requested.
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// * (In most cases, the product will be somewhat less.)
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// *
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// * Since the colormap is orthogonal, the representative value for each color
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// * component can be determined without considering the other components;
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// * then these indexes can be combined into a colormap index by a standard
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// * N-dimensional-array-subscript calculation. Most of the arithmetic involved
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// * can be precalculated and stored in the lookup table colorindex[].
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// * colorindex[i][j] maps pixel value j in component i to the nearest
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// * representative value (grid plane) for that component; this index is
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// * multiplied by the array stride for component i, so that the
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// * index of the colormap entry closest to a given pixel value is just
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// * sum( colorindex[component-number][pixel-component-value] )
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// * Aside from being fast, this scheme allows for variable spacing between
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// * representative values with no additional lookup cost.
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// *
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// * If gamma correction has been applied in color conversion, it might be wise
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// * to adjust the color grid spacing so that the representative colors are
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// * equidistant in linear space. At this writing, gamma correction is not
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// * implemented by jdcolor, so nothing is done here.
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// Declarations for ordered dithering.
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// *
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// * We use a standard 16x16 ordered dither array. The basic concept of ordered
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// * dithering is described in many references, for instance Dale Schumacher's
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// * chapter II.2 of Graphics Gems II (James Arvo, ed. Academic Press, 1991).
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// * In place of Schumacher's comparisons against a "threshold" value, we add a
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// * "dither" value to the input pixel and then round the result to the nearest
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// * output value. The dither value is equivalent to (0.5 - threshold) times
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// * the distance between output values. For ordered dithering, we assume that
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// * the output colors are equally spaced; if not, results will probably be
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// * worse, since the dither may be too much or too little at a given point.
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// *
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// * The normal calculation would be to form pixel value + dither, range-limit
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// * this to 0..MAXJSAMPLE, and then index into the colorindex table as usual.
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// * We can skip the separate range-limiting step by extending the colorindex
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// * table in both directions.
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#define ODITHER_SIZE 16 // dimension of dither matrix
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// NB: if ODITHER_SIZE is not a power of 2, ODITHER_MASK uses will break
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#define ODITHER_CELLS (ODITHER_SIZE*ODITHER_SIZE) // # cells in matrix
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#define ODITHER_MASK (ODITHER_SIZE-1) // mask for wrapping around counters
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typedef int ODITHER_MATRIX[ODITHER_SIZE][ODITHER_SIZE];
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typedef int (*ODITHER_MATRIX_PTR)[ODITHER_SIZE];
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static const UINT8 base_dither_matrix[ODITHER_SIZE][ODITHER_SIZE] = {
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// Bayer's order-4 dither array. Generated by the code given in
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// * Stephen Hawley's article "Ordered Dithering" in Graphics Gems I.
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// * The values in this array must range from 0 to ODITHER_CELLS-1.
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{ 0,192, 48,240, 12,204, 60,252, 3,195, 51,243, 15,207, 63,255 },
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{ 128, 64,176,112,140, 76,188,124,131, 67,179,115,143, 79,191,127 },
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{ 32,224, 16,208, 44,236, 28,220, 35,227, 19,211, 47,239, 31,223 },
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{ 160, 96,144, 80,172,108,156, 92,163, 99,147, 83,175,111,159, 95 },
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{ 8,200, 56,248, 4,196, 52,244, 11,203, 59,251, 7,199, 55,247 },
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{ 136, 72,184,120,132, 68,180,116,139, 75,187,123,135, 71,183,119 },
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{ 40,232, 24,216, 36,228, 20,212, 43,235, 27,219, 39,231, 23,215 },
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{ 168,104,152, 88,164,100,148, 84,171,107,155, 91,167,103,151, 87 },
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{ 2,194, 50,242, 14,206, 62,254, 1,193, 49,241, 13,205, 61,253 },
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{ 130, 66,178,114,142, 78,190,126,129, 65,177,113,141, 77,189,125 },
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{ 34,226, 18,210, 46,238, 30,222, 33,225, 17,209, 45,237, 29,221 },
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{ 162, 98,146, 82,174,110,158, 94,161, 97,145, 81,173,109,157, 93 },
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{ 10,202, 58,250, 6,198, 54,246, 9,201, 57,249, 5,197, 53,245 },
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{ 138, 74,186,122,134, 70,182,118,137, 73,185,121,133, 69,181,117 },
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{ 42,234, 26,218, 38,230, 22,214, 41,233, 25,217, 37,229, 21,213 },
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{ 170,106,154, 90,166,102,150, 86,169,105,153, 89,165,101,149, 85 }
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};
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// Declarations for Floyd-Steinberg dithering.
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// *
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// * Errors are accumulated into the array fserrors[], at a resolution of
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// * 1/16th of a pixel count. The error at a given pixel is propagated
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// * to its not-yet-processed neighbors using the standard F-S fractions,
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// * ... (here) 7/16
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// * 3/16 5/16 1/16
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// * We work left-to-right on even rows, right-to-left on odd rows.
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// *
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// * We can get away with a single array (holding one row's worth of errors)
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// * by using it to store the current row's errors at pixel columns not yet
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// * processed, but the next row's errors at columns already processed. We
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// * need only a few extra variables to hold the errors immediately around the
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// * current column. (If we are lucky, those variables are in registers, but
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// * even if not, they're probably cheaper to access than array elements are.)
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// *
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// * The fserrors[] array is indexed [component#][position].
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// * We provide (#columns + 2) entries per component; the extra entry at each
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// * end saves us from special-casing the first and last pixels.
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// *
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// * Note: on a wide image, we might not have enough room in a PC's near data
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// * segment to hold the error array; so it is allocated with alloc_large.
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#if BITS_IN_JSAMPLE == 8
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typedef INT16 FSERROR; // 16 bits should be enough
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typedef int LOCFSERROR; // use 'int' for calculation temps
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#else
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typedef INT32 FSERROR; // may need more than 16 bits
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typedef INT32 LOCFSERROR; // be sure calculation temps are big enough
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#endif
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typedef FSERROR FAR *FSERRPTR; // pointer to error array (in FAR storage!)
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// Private subobject
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#define MAX_Q_COMPS 4 // max components I can handle
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typedef struct {
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struct jpeg_color_quantizer pub; // public fields
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// Initially allocated colormap is saved here
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JSAMPARRAY sv_colormap; // The color map as a 2-D pixel array
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int sv_actual; // number of entries in use
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JSAMPARRAY colorindex; // Precomputed mapping for speed
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// colorindex[i][j] = index of color closest to pixel value j in component i,
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// * premultiplied as described above. Since colormap indexes must fit into
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// * JSAMPLEs, the entries of this array will too.
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boolean is_padded; // is the colorindex padded for odither?
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int Ncolors[MAX_Q_COMPS]; // # of values alloced to each component
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// Variables for ordered dithering
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int row_index; // cur row's vertical index in dither matrix
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ODITHER_MATRIX_PTR odither[MAX_Q_COMPS]; // one dither array per component
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// Variables for Floyd-Steinberg dithering
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FSERRPTR fserrors[MAX_Q_COMPS]; // accumulated errors
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boolean on_odd_row; // flag to remember which row we are on
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} my_cquantizer;
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typedef my_cquantizer * my_cquantize_ptr;
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// * Policy-making subroutines for create_colormap and create_colorindex.
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// * These routines determine the colormap to be used. The rest of the module
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// * only assumes that the colormap is orthogonal.
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// *
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// * * select_ncolors decides how to divvy up the available colors
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// * among the components.
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// * * output_value defines the set of representative values for a component.
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// * * largest_input_value defines the mapping from input values to
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// * representative values for a component.
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// * Note that the latter two routines may impose different policies for
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// * different components, though this is not currently done.
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LOCAL int
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select_ncolors (j_decompress_ptr cinfo, int Ncolors[])
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// Determine allocation of desired colors to components,
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// and fill in Ncolors[] array to indicate choice.
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// Return value is total number of colors (product of Ncolors[] values).
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{
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int nc = cinfo->out_color_components; // number of color components
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int max_colors = cinfo->desired_number_of_colors;
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int total_colors, iroot, i, j;
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boolean changed;
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LONG temp;
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static const int RGB_order[3] = { RGB_GREEN, RGB_RED, RGB_BLUE };
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// We can allocate at least the nc'th root of max_colors per component.
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// Compute floor(nc'th root of max_colors).
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iroot = 1;
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do {
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iroot++;
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temp = iroot; // set temp = iroot ** nc
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for (i = 1; i < nc; i++)
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temp *= iroot;
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} while (temp <= (LONG) max_colors); // repeat till iroot exceeds root
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iroot--; // now iroot = floor(root)
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// Must have at least 2 color values per component
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if (iroot < 2)
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ERREXIT1(cinfo, JERR_QUANT_FEW_COLORS, (int) temp);
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// Initialize to iroot color values for each component
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total_colors = 1;
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for (i = 0; i < nc; i++) {
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Ncolors[i] = iroot;
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total_colors *= iroot;
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}
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// We may be able to increment the count for one or more components without
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// * exceeding max_colors, though we know not all can be incremented.
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// * Sometimes, the first component can be incremented more than once!
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// * (Example: for 16 colors, we start at 2*2*2, go to 3*2*2, then 4*2*2.)
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// * In RGB colorspace, try to increment G first, then R, then B.
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do {
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changed = FALSE;
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for (i = 0; i < nc; i++) {
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j = (cinfo->out_color_space == JCS_RGB ? RGB_order[i] : i);
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// calculate new total_colors if Ncolors[j] is incremented
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temp = total_colors / Ncolors[j];
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temp *= Ncolors[j]+1; // done in long arith to avoid oflo
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if (temp > (LONG) max_colors)
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break; // won't fit, done with this pass
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Ncolors[j]++; // OK, apply the increment
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total_colors = (int) temp;
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changed = TRUE;
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}
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} while (changed);
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return total_colors;
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}
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LOCAL int
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output_value (j_decompress_ptr cinfo, int ci, int j, int maxj)
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// Return j'th output value, where j will range from 0 to maxj
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// The output values must fall in 0..MAXJSAMPLE in increasing order
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{
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// We always provide values 0 and MAXJSAMPLE for each component;
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// * any additional values are equally spaced between these limits.
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// * (Forcing the upper and lower values to the limits ensures that
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// * dithering can't produce a color outside the selected gamut.)
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return (int) (((INT32) j * MAXJSAMPLE + maxj/2) / maxj);
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}
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LOCAL int
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largest_input_value (j_decompress_ptr cinfo, int ci, int j, int maxj)
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// Return largest input value that should map to j'th output value
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// Must have largest(j=0) >= 0, and largest(j=maxj) >= MAXJSAMPLE
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{
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// Breakpoints are halfway between values returned by output_value
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return (int) (((INT32) (2*j + 1) * MAXJSAMPLE + maxj) / (2*maxj));
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}
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// * Create the colormap.
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LOCAL void
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create_colormap (j_decompress_ptr cinfo)
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{
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my_cquantize_ptr cquantize = (my_cquantize_ptr) cinfo->cquantize;
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JSAMPARRAY colormap; // Created colormap
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int total_colors; // Number of distinct output colors
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int i,j,k, nci, blksize, blkdist, ptr, val;
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// Select number of colors for each component
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total_colors = select_ncolors(cinfo, cquantize->Ncolors);
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// Report selected color counts
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if (cinfo->out_color_components == 3)
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TRACEMS4(cinfo, 1, JTRC_QUANT_3_NCOLORS,
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total_colors, cquantize->Ncolors[0],
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cquantize->Ncolors[1], cquantize->Ncolors[2]);
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else
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TRACEMS1(cinfo, 1, JTRC_QUANT_NCOLORS, total_colors);
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// Allocate and fill in the colormap.
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// The colors are ordered in the map in standard row-major order,
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// i.e. rightmost (highest-indexed) color changes most rapidly.
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colormap = (*cinfo->mem->alloc_sarray)
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((j_common_ptr) cinfo, JPOOL_IMAGE,
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(JDIMENSION) total_colors, (JDIMENSION) cinfo->out_color_components);
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// blksize is number of adjacent repeated entries for a component
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// blkdist is distance between groups of identical entries for a component
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blkdist = total_colors;
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for (i = 0; i < cinfo->out_color_components; i++) {
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// fill in colormap entries for i'th color component
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nci = cquantize->Ncolors[i]; // # of distinct values for this color
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blksize = blkdist / nci;
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for (j = 0; j < nci; j++) {
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// Compute j'th output value (out of nci) for component
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val = output_value(cinfo, i, j, nci-1);
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// Fill in all colormap entries that have this value of this component
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for (ptr = j * blksize; ptr < total_colors; ptr += blkdist) {
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// fill in blksize entries beginning at ptr
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for (k = 0; k < blksize; k++)
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colormap[i][ptr+k] = (JSAMPLE) val;
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}
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}
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blkdist = blksize; // blksize of this color is blkdist of next
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}
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// Save the colormap in private storage,
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// * where it will survive color quantization mode changes.
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cquantize->sv_colormap = colormap;
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cquantize->sv_actual = total_colors;
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}
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// * Create the color index table.
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LOCAL void
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create_colorindex (j_decompress_ptr cinfo)
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{
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my_cquantize_ptr cquantize = (my_cquantize_ptr) cinfo->cquantize;
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JSAMPROW indexptr;
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int i,j,k, nci, blksize, val, pad;
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// For ordered dither, we pad the color index tables by MAXJSAMPLE in
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// * each direction (input index values can be -MAXJSAMPLE .. 2*MAXJSAMPLE).
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// * This is not necessary in the other dithering modes. However, we
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// * flag whether it was done in case user changes dithering mode.
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if (cinfo->dither_mode == JDITHER_ORDERED) {
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pad = MAXJSAMPLE*2;
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cquantize->is_padded = TRUE;
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} else {
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pad = 0;
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cquantize->is_padded = FALSE;
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}
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cquantize->colorindex = (*cinfo->mem->alloc_sarray)
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((j_common_ptr) cinfo, JPOOL_IMAGE,
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(JDIMENSION) (MAXJSAMPLE+1 + pad),
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(JDIMENSION) cinfo->out_color_components);
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// blksize is number of adjacent repeated entries for a component
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blksize = cquantize->sv_actual;
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for (i = 0; i < cinfo->out_color_components; i++) {
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// fill in colorindex entries for i'th color component
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nci = cquantize->Ncolors[i]; // # of distinct values for this color
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blksize = blksize / nci;
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// adjust colorindex pointers to provide padding at negative indexes.
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if (pad)
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cquantize->colorindex[i] += MAXJSAMPLE;
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// in loop, val = index of current output value,
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// and k = largest j that maps to current val
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indexptr = cquantize->colorindex[i];
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val = 0;
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k = largest_input_value(cinfo, i, 0, nci-1);
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for (j = 0; j <= MAXJSAMPLE; j++) {
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while (j > k) // advance val if past boundary
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k = largest_input_value(cinfo, i, ++val, nci-1);
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// premultiply so that no multiplication needed in main processing
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indexptr[j] = (JSAMPLE) (val * blksize);
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}
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// Pad at both ends if necessary
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if (pad)
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for (j = 1; j <= MAXJSAMPLE; j++) {
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indexptr[-j] = indexptr[0];
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indexptr[MAXJSAMPLE+j] = indexptr[MAXJSAMPLE];
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}
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}
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}
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// * Create an ordered-dither array for a component having ncolors
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// * distinct output values.
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LOCAL ODITHER_MATRIX_PTR
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make_odither_array (j_decompress_ptr cinfo, int ncolors)
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{
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ODITHER_MATRIX_PTR odither;
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int j,k;
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INT32 num,den;
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odither = (ODITHER_MATRIX_PTR)
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(*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE,
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SIZEOF(ODITHER_MATRIX));
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// The inter-value distance for this color is MAXJSAMPLE/(ncolors-1).
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// * Hence the dither value for the matrix cell with fill order f
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// * (f=0..N-1) should be (N-1-2*f)/(2*N) * MAXJSAMPLE/(ncolors-1).
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// * On 16-bit-int machine, be careful to avoid overflow.
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den = 2 * ODITHER_CELLS * ((INT32) (ncolors - 1));
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for (j = 0; j < ODITHER_SIZE; j++) {
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for (k = 0; k < ODITHER_SIZE; k++) {
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num = ((INT32) (ODITHER_CELLS-1 - 2*((int)base_dither_matrix[j][k])))
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* MAXJSAMPLE;
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// Ensure round towards zero despite C's lack of consistency
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// * about rounding negative values in integer division...
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odither[j][k] = (int) (num<0 ? -((-num)/den) : num/den);
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}
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}
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return odither;
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}
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// * Create the ordered-dither tables.
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// * Components having the same number of representative colors may
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// * share a dither table.
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LOCAL void
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create_odither_tables (j_decompress_ptr cinfo)
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{
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my_cquantize_ptr cquantize = (my_cquantize_ptr) cinfo->cquantize;
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ODITHER_MATRIX_PTR odither;
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int i, j, nci;
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for (i = 0; i < cinfo->out_color_components; i++) {
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nci = cquantize->Ncolors[i]; // # of distinct values for this color
|
|
odither = NULL; // search for matching prior component
|
|
for (j = 0; j < i; j++) {
|
|
if (nci == cquantize->Ncolors[j]) {
|
|
odither = cquantize->odither[j];
|
|
break;
|
|
}
|
|
}
|
|
if (odither == NULL) // need a new table?
|
|
odither = make_odither_array(cinfo, nci);
|
|
cquantize->odither[i] = odither;
|
|
}
|
|
}
|
|
|
|
|
|
// * Map some rows of pixels to the output colormapped representation.
|
|
|
|
METHODDEF void
|
|
color_quantize (j_decompress_ptr cinfo, JSAMPARRAY input_buf,
|
|
JSAMPARRAY output_buf, int num_rows)
|
|
// General case, no dithering
|
|
{
|
|
my_cquantize_ptr cquantize = (my_cquantize_ptr) cinfo->cquantize;
|
|
JSAMPARRAY colorindex = cquantize->colorindex;
|
|
register int pixcode, ci;
|
|
register JSAMPROW ptrin, ptrout;
|
|
int row;
|
|
JDIMENSION col;
|
|
JDIMENSION width = cinfo->output_width;
|
|
register int nc = cinfo->out_color_components;
|
|
|
|
for (row = 0; row < num_rows; row++) {
|
|
ptrin = input_buf[row];
|
|
ptrout = output_buf[row];
|
|
for (col = width; col > 0; col--) {
|
|
pixcode = 0;
|
|
for (ci = 0; ci < nc; ci++) {
|
|
pixcode += GETJSAMPLE(colorindex[ci][GETJSAMPLE(*ptrin++)]);
|
|
}
|
|
*ptrout++ = (JSAMPLE) pixcode;
|
|
}
|
|
}
|
|
}
|
|
|
|
|
|
METHODDEF void
|
|
color_quantize3 (j_decompress_ptr cinfo, JSAMPARRAY input_buf,
|
|
JSAMPARRAY output_buf, int num_rows)
|
|
// Fast path for out_color_components==3, no dithering
|
|
{
|
|
my_cquantize_ptr cquantize = (my_cquantize_ptr) cinfo->cquantize;
|
|
register int pixcode;
|
|
register JSAMPROW ptrin, ptrout;
|
|
JSAMPROW colorindex0 = cquantize->colorindex[0];
|
|
JSAMPROW colorindex1 = cquantize->colorindex[1];
|
|
JSAMPROW colorindex2 = cquantize->colorindex[2];
|
|
int row;
|
|
JDIMENSION col;
|
|
JDIMENSION width = cinfo->output_width;
|
|
|
|
for (row = 0; row < num_rows; row++) {
|
|
ptrin = input_buf[row];
|
|
ptrout = output_buf[row];
|
|
for (col = width; col > 0; col--) {
|
|
pixcode = GETJSAMPLE(colorindex0[GETJSAMPLE(*ptrin++)]);
|
|
pixcode += GETJSAMPLE(colorindex1[GETJSAMPLE(*ptrin++)]);
|
|
pixcode += GETJSAMPLE(colorindex2[GETJSAMPLE(*ptrin++)]);
|
|
*ptrout++ = (JSAMPLE) pixcode;
|
|
}
|
|
}
|
|
}
|
|
|
|
|
|
METHODDEF void
|
|
quantize_ord_dither (j_decompress_ptr cinfo, JSAMPARRAY input_buf,
|
|
JSAMPARRAY output_buf, int num_rows)
|
|
// General case, with ordered dithering
|
|
{
|
|
my_cquantize_ptr cquantize = (my_cquantize_ptr) cinfo->cquantize;
|
|
register JSAMPROW input_ptr;
|
|
register JSAMPROW output_ptr;
|
|
JSAMPROW colorindex_ci;
|
|
int * dither; // points to active row of dither matrix
|
|
int row_index, col_index; // current indexes into dither matrix
|
|
int nc = cinfo->out_color_components;
|
|
int ci;
|
|
int row;
|
|
JDIMENSION col;
|
|
JDIMENSION width = cinfo->output_width;
|
|
|
|
for (row = 0; row < num_rows; row++) {
|
|
// Initialize output values to 0 so can process components separately
|
|
jzero_far((void FAR *) output_buf[row],
|
|
(size_t) (width * SIZEOF(JSAMPLE)));
|
|
row_index = cquantize->row_index;
|
|
for (ci = 0; ci < nc; ci++) {
|
|
input_ptr = input_buf[row] + ci;
|
|
output_ptr = output_buf[row];
|
|
colorindex_ci = cquantize->colorindex[ci];
|
|
dither = cquantize->odither[ci][row_index];
|
|
col_index = 0;
|
|
|
|
for (col = width; col > 0; col--) {
|
|
// Form pixel value + dither, range-limit to 0..MAXJSAMPLE,
|
|
// * select output value, accumulate into output code for this pixel.
|
|
// * Range-limiting need not be done explicitly, as we have extended
|
|
// * the colorindex table to produce the right answers for out-of-range
|
|
// * inputs. The maximum dither is +- MAXJSAMPLE; this sets the
|
|
// * required amount of padding.
|
|
*output_ptr += colorindex_ci[GETJSAMPLE(*input_ptr)+dither[col_index]];
|
|
input_ptr += nc;
|
|
output_ptr++;
|
|
col_index = (col_index + 1) & ODITHER_MASK;
|
|
}
|
|
}
|
|
// Advance row index for next row
|
|
row_index = (row_index + 1) & ODITHER_MASK;
|
|
cquantize->row_index = row_index;
|
|
}
|
|
}
|
|
|
|
|
|
METHODDEF void
|
|
quantize3_ord_dither (j_decompress_ptr cinfo, JSAMPARRAY input_buf,
|
|
JSAMPARRAY output_buf, int num_rows)
|
|
// Fast path for out_color_components==3, with ordered dithering
|
|
{
|
|
my_cquantize_ptr cquantize = (my_cquantize_ptr) cinfo->cquantize;
|
|
register int pixcode;
|
|
register JSAMPROW input_ptr;
|
|
register JSAMPROW output_ptr;
|
|
JSAMPROW colorindex0 = cquantize->colorindex[0];
|
|
JSAMPROW colorindex1 = cquantize->colorindex[1];
|
|
JSAMPROW colorindex2 = cquantize->colorindex[2];
|
|
int * dither0; // points to active row of dither matrix
|
|
int * dither1;
|
|
int * dither2;
|
|
int row_index, col_index; // current indexes into dither matrix
|
|
int row;
|
|
JDIMENSION col;
|
|
JDIMENSION width = cinfo->output_width;
|
|
|
|
for (row = 0; row < num_rows; row++) {
|
|
row_index = cquantize->row_index;
|
|
input_ptr = input_buf[row];
|
|
output_ptr = output_buf[row];
|
|
dither0 = cquantize->odither[0][row_index];
|
|
dither1 = cquantize->odither[1][row_index];
|
|
dither2 = cquantize->odither[2][row_index];
|
|
col_index = 0;
|
|
|
|
for (col = width; col > 0; col--) {
|
|
pixcode = GETJSAMPLE(colorindex0[GETJSAMPLE(*input_ptr++) +
|
|
dither0[col_index]]);
|
|
pixcode += GETJSAMPLE(colorindex1[GETJSAMPLE(*input_ptr++) +
|
|
dither1[col_index]]);
|
|
pixcode += GETJSAMPLE(colorindex2[GETJSAMPLE(*input_ptr++) +
|
|
dither2[col_index]]);
|
|
*output_ptr++ = (JSAMPLE) pixcode;
|
|
col_index = (col_index + 1) & ODITHER_MASK;
|
|
}
|
|
row_index = (row_index + 1) & ODITHER_MASK;
|
|
cquantize->row_index = row_index;
|
|
}
|
|
}
|
|
|
|
|
|
METHODDEF void
|
|
quantize_fs_dither (j_decompress_ptr cinfo, JSAMPARRAY input_buf,
|
|
JSAMPARRAY output_buf, int num_rows)
|
|
// General case, with Floyd-Steinberg dithering
|
|
{
|
|
my_cquantize_ptr cquantize = (my_cquantize_ptr) cinfo->cquantize;
|
|
register LOCFSERROR cur; // current error or pixel value
|
|
LOCFSERROR belowerr; // error for pixel below cur
|
|
LOCFSERROR bpreverr; // error for below/prev col
|
|
LOCFSERROR bnexterr; // error for below/next col
|
|
LOCFSERROR delta;
|
|
register FSERRPTR errorptr; // => fserrors[] at column before current
|
|
register JSAMPROW input_ptr;
|
|
register JSAMPROW output_ptr;
|
|
JSAMPROW colorindex_ci;
|
|
JSAMPROW colormap_ci;
|
|
int pixcode;
|
|
int nc = cinfo->out_color_components;
|
|
int dir; // 1 for left-to-right, -1 for right-to-left
|
|
int dirnc; // dir * nc
|
|
int ci;
|
|
int row;
|
|
JDIMENSION col;
|
|
JDIMENSION width = cinfo->output_width;
|
|
JSAMPLE *range_limit = cinfo->sample_range_limit;
|
|
SHIFT_TEMPS
|
|
|
|
for (row = 0; row < num_rows; row++) {
|
|
// Initialize output values to 0 so can process components separately
|
|
jzero_far((void FAR *) output_buf[row],
|
|
(size_t) (width * SIZEOF(JSAMPLE)));
|
|
for (ci = 0; ci < nc; ci++) {
|
|
input_ptr = input_buf[row] + ci;
|
|
output_ptr = output_buf[row];
|
|
if (cquantize->on_odd_row) {
|
|
// work right to left in this row
|
|
input_ptr += (width-1) * nc; // so point to rightmost pixel
|
|
output_ptr += width-1;
|
|
dir = -1;
|
|
dirnc = -nc;
|
|
errorptr = cquantize->fserrors[ci] + (width+1); // => entry after last column
|
|
} else {
|
|
// work left to right in this row
|
|
dir = 1;
|
|
dirnc = nc;
|
|
errorptr = cquantize->fserrors[ci]; // => entry before first column
|
|
}
|
|
colorindex_ci = cquantize->colorindex[ci];
|
|
colormap_ci = cquantize->sv_colormap[ci];
|
|
// Preset error values: no error propagated to first pixel from left
|
|
cur = 0;
|
|
// and no error propagated to row below yet
|
|
belowerr = bpreverr = 0;
|
|
|
|
for (col = width; col > 0; col--) {
|
|
// cur holds the error propagated from the previous pixel on the
|
|
// * current line. Add the error propagated from the previous line
|
|
// * to form the complete error correction term for this pixel, and
|
|
// * round the error term (which is expressed * 16) to an integer.
|
|
// * RIGHT_SHIFT rounds towards minus infinity, so adding 8 is correct
|
|
// * for either sign of the error value.
|
|
// * Note: errorptr points to *previous* column's array entry.
|
|
cur = RIGHT_SHIFT(cur + errorptr[dir] + 8, 4);
|
|
// Form pixel value + error, and range-limit to 0..MAXJSAMPLE.
|
|
// * The maximum error is +- MAXJSAMPLE; this sets the required size
|
|
// * of the range_limit array.
|
|
cur += GETJSAMPLE(*input_ptr);
|
|
cur = GETJSAMPLE(range_limit[cur]);
|
|
// Select output value, accumulate into output code for this pixel
|
|
pixcode = GETJSAMPLE(colorindex_ci[cur]);
|
|
*output_ptr += (JSAMPLE) pixcode;
|
|
// Compute actual representation error at this pixel
|
|
// Note: we can do this even though we don't have the final
|
|
// pixel code, because the colormap is orthogonal.
|
|
cur -= GETJSAMPLE(colormap_ci[pixcode]);
|
|
// Compute error fractions to be propagated to adjacent pixels.
|
|
// * Add these into the running sums, and simultaneously shift the
|
|
// * next-line error sums left by 1 column.
|
|
bnexterr = cur;
|
|
delta = cur * 2;
|
|
cur += delta; // form error * 3
|
|
errorptr[0] = (FSERROR) (bpreverr + cur);
|
|
cur += delta; // form error * 5
|
|
bpreverr = belowerr + cur;
|
|
belowerr = bnexterr;
|
|
cur += delta; // form error * 7
|
|
// At this point cur contains the 7/16 error value to be propagated
|
|
// * to the next pixel on the current line, and all the errors for the
|
|
// * next line have been shifted over. We are therefore ready to move on.
|
|
input_ptr += dirnc; // advance input ptr to next column
|
|
output_ptr += dir; // advance output ptr to next column
|
|
errorptr += dir; // advance errorptr to current column
|
|
}
|
|
// Post-loop cleanup: we must unload the final error value into the
|
|
// * final fserrors[] entry. Note we need not unload belowerr because
|
|
// * it is for the dummy column before or after the actual array.
|
|
errorptr[0] = (FSERROR) bpreverr; // unload prev err into array
|
|
}
|
|
cquantize->on_odd_row = (cquantize->on_odd_row ? FALSE : TRUE);
|
|
}
|
|
}
|
|
|
|
|
|
// * Allocate workspace for Floyd-Steinberg errors.
|
|
|
|
LOCAL void
|
|
alloc_fs_workspace (j_decompress_ptr cinfo)
|
|
{
|
|
my_cquantize_ptr cquantize = (my_cquantize_ptr) cinfo->cquantize;
|
|
size_t arraysize;
|
|
int i;
|
|
|
|
arraysize = (size_t) ((cinfo->output_width + 2) * SIZEOF(FSERROR));
|
|
for (i = 0; i < cinfo->out_color_components; i++) {
|
|
cquantize->fserrors[i] = (FSERRPTR)
|
|
(*cinfo->mem->alloc_large)((j_common_ptr) cinfo, JPOOL_IMAGE, arraysize);
|
|
}
|
|
}
|
|
|
|
|
|
// * Initialize for one-pass color quantization.
|
|
|
|
METHODDEF void
|
|
start_pass_1_quant (j_decompress_ptr cinfo, boolean is_pre_scan)
|
|
{
|
|
my_cquantize_ptr cquantize = (my_cquantize_ptr) cinfo->cquantize;
|
|
size_t arraysize;
|
|
int i;
|
|
|
|
// Install my colormap.
|
|
cinfo->colormap = cquantize->sv_colormap;
|
|
cinfo->actual_number_of_colors = cquantize->sv_actual;
|
|
|
|
// Initialize for desired dithering mode.
|
|
switch (cinfo->dither_mode) {
|
|
case JDITHER_NONE:
|
|
if (cinfo->out_color_components == 3)
|
|
cquantize->pub.color_quantize = color_quantize3;
|
|
else
|
|
cquantize->pub.color_quantize = color_quantize;
|
|
break;
|
|
case JDITHER_ORDERED:
|
|
if (cinfo->out_color_components == 3)
|
|
cquantize->pub.color_quantize = quantize3_ord_dither;
|
|
else
|
|
cquantize->pub.color_quantize = quantize_ord_dither;
|
|
cquantize->row_index = 0; // initialize state for ordered dither
|
|
// If user changed to ordered dither from another mode,
|
|
// * we must recreate the color index table with padding.
|
|
// * This will cost extra space, but probably isn't very likely.
|
|
if (! cquantize->is_padded)
|
|
create_colorindex(cinfo);
|
|
// Create ordered-dither tables if we didn't already.
|
|
if (cquantize->odither[0] == NULL)
|
|
create_odither_tables(cinfo);
|
|
break;
|
|
case JDITHER_FS:
|
|
cquantize->pub.color_quantize = quantize_fs_dither;
|
|
cquantize->on_odd_row = FALSE; // initialize state for F-S dither
|
|
// Allocate Floyd-Steinberg workspace if didn't already.
|
|
if (cquantize->fserrors[0] == NULL)
|
|
alloc_fs_workspace(cinfo);
|
|
// Initialize the propagated errors to zero.
|
|
arraysize = (size_t) ((cinfo->output_width + 2) * SIZEOF(FSERROR));
|
|
for (i = 0; i < cinfo->out_color_components; i++)
|
|
jzero_far((void FAR *) cquantize->fserrors[i], arraysize);
|
|
break;
|
|
default:
|
|
ERREXIT(cinfo, JERR_NOT_COMPILED);
|
|
break;
|
|
}
|
|
}
|
|
|
|
|
|
// * Finish up at the end of the pass.
|
|
|
|
METHODDEF void
|
|
finish_pass_1_quant (j_decompress_ptr cinfo)
|
|
{
|
|
// no work in 1-pass case
|
|
}
|
|
|
|
|
|
// * Switch to a new external colormap between output passes.
|
|
// * Shouldn't get to this module!
|
|
|
|
METHODDEF void
|
|
new_color_map_1_quant (j_decompress_ptr cinfo)
|
|
{
|
|
ERREXIT(cinfo, JERR_MODE_CHANGE);
|
|
}
|
|
|
|
|
|
// * Module initialization routine for 1-pass color quantization.
|
|
|
|
GLOBAL void
|
|
jinit_1pass_quantizer (j_decompress_ptr cinfo)
|
|
{
|
|
my_cquantize_ptr cquantize;
|
|
|
|
cquantize = (my_cquantize_ptr)
|
|
(*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE,
|
|
SIZEOF(my_cquantizer));
|
|
cinfo->cquantize = (struct jpeg_color_quantizer *) cquantize;
|
|
cquantize->pub.start_pass = start_pass_1_quant;
|
|
cquantize->pub.finish_pass = finish_pass_1_quant;
|
|
cquantize->pub.new_color_map = new_color_map_1_quant;
|
|
cquantize->fserrors[0] = NULL; // Flag FS workspace not allocated
|
|
cquantize->odither[0] = NULL; // Also flag odither arrays not allocated
|
|
|
|
// Make sure my internal arrays won't overflow
|
|
if (cinfo->out_color_components > MAX_Q_COMPS)
|
|
ERREXIT1(cinfo, JERR_QUANT_COMPONENTS, MAX_Q_COMPS);
|
|
// Make sure colormap indexes can be represented by JSAMPLEs
|
|
if (cinfo->desired_number_of_colors > (MAXJSAMPLE+1))
|
|
ERREXIT1(cinfo, JERR_QUANT_MANY_COLORS, MAXJSAMPLE+1);
|
|
|
|
// Create the colormap and color index table.
|
|
create_colormap(cinfo);
|
|
create_colorindex(cinfo);
|
|
|
|
// Allocate Floyd-Steinberg workspace now if requested.
|
|
// * We do this now since it is FAR storage and may affect the memory
|
|
// * manager's space calculations. If the user changes to FS dither
|
|
// * mode in a later pass, we will allocate the space then, and will
|
|
// * possibly overrun the max_memory_to_use setting.
|
|
if (cinfo->dither_mode == JDITHER_FS)
|
|
alloc_fs_workspace(cinfo);
|
|
}
|
|
|
|
#endif // QUANT_1PASS_SUPPORTED
|
|
|
|
|
|
#ifdef _MSC_VER
|
|
#pragma warning(pop)
|
|
#endif
|