/* * The Python Imaging Library * $Id$ * * imaging palette object * * history: * 1996-05-05 fl Added to library * 1996-05-27 fl Added colour mapping stuff * 1997-05-12 fl Support RGBA palettes * 2005-02-09 fl Removed grayscale entries from web palette * * Copyright (c) Secret Labs AB 1997-2005. All rights reserved. * Copyright (c) Fredrik Lundh 1995-1997. * * See the README file for information on usage and redistribution. */ #include "Imaging.h" #include ImagingPalette ImagingPaletteNew(const char* mode) { /* Create a palette object */ int i; ImagingPalette palette; if (strcmp(mode, "RGB") && strcmp(mode, "RGBA")) return (ImagingPalette) ImagingError_ModeError(); palette = calloc(1, sizeof(struct ImagingPaletteInstance)); if (!palette) return (ImagingPalette) ImagingError_MemoryError(); strncpy(palette->mode, mode, IMAGING_MODE_LENGTH); /* Initialize to ramp */ for (i = 0; i < 256; i++) { palette->palette[i*4+0] = palette->palette[i*4+1] = palette->palette[i*4+2] = (UINT8) i; palette->palette[i*4+3] = 255; /* opaque */ } return palette; } ImagingPalette ImagingPaletteNewBrowser(void) { /* Create a standard "browser" palette object */ int i, r, g, b; ImagingPalette palette; palette = ImagingPaletteNew("RGB"); if (!palette) return NULL; /* Blank out unused entries */ /* FIXME: Add 10-level windows palette here? */ for (i = 0; i < 10; i++) { palette->palette[i*4+0] = palette->palette[i*4+1] = palette->palette[i*4+2] = 0; } /* Simple 6x6x6 colour cube */ for (b = 0; b < 256; b += 51) for (g = 0; g < 256; g += 51) for (r = 0; r < 256; r += 51) { palette->palette[i*4+0] = r; palette->palette[i*4+1] = g; palette->palette[i*4+2] = b; i++; } /* Blank out unused entries */ /* FIXME: add 30-level greyscale wedge here? */ for (; i < 256; i++) { palette->palette[i*4+0] = palette->palette[i*4+1] = palette->palette[i*4+2] = 0; } return palette; } ImagingPalette ImagingPaletteDuplicate(ImagingPalette palette) { /* Duplicate palette descriptor */ ImagingPalette new_palette; if (!palette) return NULL; /* malloc check ok, small constant allocation */ new_palette = malloc(sizeof(struct ImagingPaletteInstance)); if (!new_palette) return (ImagingPalette) ImagingError_MemoryError(); memcpy(new_palette, palette, sizeof(struct ImagingPaletteInstance)); /* Don't share the cache */ new_palette->cache = NULL; return new_palette; } void ImagingPaletteDelete(ImagingPalette palette) { /* Destroy palette object */ if (palette) { if (palette->cache) free(palette->cache); free(palette); } } /* -------------------------------------------------------------------- */ /* Colour mapping */ /* -------------------------------------------------------------------- */ /* This code is used to map RGB triplets to palette indices, using a palette index cache. */ /* * This implementation is loosely based on the corresponding code in * the IJG JPEG library by Thomas G. Lane. Original algorithms by * Paul Heckbert and Spencer W. Thomas. * * The IJG JPEG library is copyright (C) 1991-1995, Thomas G. Lane. */ #define DIST(a, b, s) (a - b) * (a - b) * s /* Colour weights (no scaling, for now) */ #define RSCALE 1 #define GSCALE 1 #define BSCALE 1 /* Calculated scaled distances */ #define RDIST(a, b) DIST(a, b, RSCALE*RSCALE) #define GDIST(a, b) DIST(a, b, GSCALE*GSCALE) #define BDIST(a, b) DIST(a, b, BSCALE*BSCALE) /* Incremental steps */ #define RSTEP (4 * RSCALE) #define GSTEP (4 * GSCALE) #define BSTEP (4 * BSCALE) #define BOX 8 #define BOXVOLUME BOX*BOX*BOX void ImagingPaletteCacheUpdate(ImagingPalette palette, int r, int g, int b) { int i, j; unsigned int dmin[256], dmax; int r0, g0, b0; int r1, g1, b1; int rc, gc, bc; unsigned int d[BOXVOLUME]; UINT8 c[BOXVOLUME]; /* Get box boundaries for the given (r,g,b)-triplet. Each box covers eight cache slots (32 colour values, that is). */ r0 = r & 0xe0; r1 = r0 + 0x1f; rc = (r0 + r1) / 2; g0 = g & 0xe0; g1 = g0 + 0x1f; gc = (g0 + g1) / 2; b0 = b & 0xe0; b1 = b0 + 0x1f; bc = (b0 + b1) / 2; /* Step 1 -- Select relevant palette entries (after Heckbert) */ /* For each palette entry, calculate the min and max distances to * any position in the box given by the colour we're looking for. */ dmax = (unsigned int) ~0; for (i = 0; i < 256; i++) { int r, g, b; unsigned int tmin, tmax; /* Find min and max distances to any point in the box */ r = palette->palette[i*4+0]; tmin = (r < r0) ? RDIST(r, r1) : (r > r1) ? RDIST(r, r0) : 0; tmax = (r <= rc) ? RDIST(r, r1) : RDIST(r, r0); g = palette->palette[i*4+1]; tmin += (g < g0) ? GDIST(g, g1) : (g > g1) ? GDIST(g, g0) : 0; tmax += (g <= gc) ? GDIST(g, g1) : GDIST(g, g0); b = palette->palette[i*4+2]; tmin += (b < b0) ? BDIST(b, b1) : (b > b1) ? BDIST(b, b0) : 0; tmax += (b <= bc) ? BDIST(b, b1) : BDIST(b, b0); dmin[i] = tmin; if (tmax < dmax) dmax = tmax; /* keep the smallest max distance only */ } /* Step 2 -- Incrementally update cache slot (after Thomas) */ /* Find the box containing the nearest palette entry, and update * all slots in that box. We only check boxes for which the min * distance is less than or equal the smallest max distance */ for (i = 0; i < BOXVOLUME; i++) d[i] = (unsigned int) ~0; for (i = 0; i < 256; i++) if (dmin[i] <= dmax) { int rd, gd, bd; int ri, gi, bi; int rx, gx, bx; ri = (r0 - palette->palette[i*4+0]) * RSCALE; gi = (g0 - palette->palette[i*4+1]) * GSCALE; bi = (b0 - palette->palette[i*4+2]) * BSCALE; rd = ri*ri + gi*gi + bi*bi; ri = ri * (2 * RSTEP) + RSTEP * RSTEP; gi = gi * (2 * GSTEP) + GSTEP * GSTEP; bi = bi * (2 * BSTEP) + BSTEP * BSTEP; rx = ri; for (r = j = 0; r < BOX; r++) { gd = rd; gx = gi; for (g = 0; g < BOX; g++) { bd = gd; bx = bi; for (b = 0; b < BOX; b++) { if ((unsigned int) bd < d[j]) { d[j] = bd; c[j] = (UINT8) i; } bd += bx; bx += 2 * BSTEP * BSTEP; j++; } gd += gx; gx += 2 * GSTEP * GSTEP; } rd += rx; rx += 2 * RSTEP * RSTEP; } } /* Step 3 -- Update cache */ /* The c array now contains the closest match for each * cache slot in the box. Update the cache. */ j = 0; for (r = r0; r < r1; r+=4) for (g = g0; g < g1; g+=4) for (b = b0; b < b1; b+=4) ImagingPaletteCache(palette, r, g, b) = c[j++]; } int ImagingPaletteCachePrepare(ImagingPalette palette) { /* Add a colour cache to a palette */ int i; int entries = 64*64*64; if (palette->cache == NULL) { /* The cache is 512k. It might be a good idea to break it up into a pointer array (e.g. an 8-bit image?) */ /* malloc check ok, small constant allocation */ palette->cache = (INT16*) malloc(entries * sizeof(INT16)); if (!palette->cache) { (void) ImagingError_MemoryError(); return -1; } /* Mark all entries as empty */ for (i = 0; i < entries; i++) palette->cache[i] = 0x100; } return 0; } void ImagingPaletteCacheDelete(ImagingPalette palette) { /* Release the colour cache, if any */ if (palette && palette->cache) { free(palette->cache); palette->cache = NULL; } }