--- /dev/null
+//
+// gif.h
+// by Charlie Tangora
+// Public domain.
+// Email me : ctangora -at- gmail -dot- com
+//
+// This file offers a simple, very limited way to create animated GIFs directly in code.
+//
+// Those looking for particular cleverness are likely to be disappointed; it's pretty
+// much a straight-ahead implementation of the GIF format with optional Floyd-Steinberg
+// dithering. (It does at least use delta encoding - only the changed portions of each
+// frame are saved.)
+//
+// So resulting files are often quite large. The hope is that it will be handy nonetheless
+// as a quick and easily-integrated way for programs to spit out animations.
+//
+// Only RGBA8 is currently supported as an input format. (The alpha is ignored.)
+//
+// If capturing a buffer with a bottom-left origin (such as OpenGL), define GIF_FLIP_VERT
+// to automatically flip the buffer data when writing the image (the buffer itself is
+// unchanged.
+//
+// USAGE:
+// Create a GifWriter struct. Pass it to GifBegin() to initialize and write the header.
+// Pass subsequent frames to GifWriteFrame().
+// Finally, call GifEnd() to close the file handle and free memory.
+//
+
+#ifndef gif_h
+#define gif_h
+
+#include <stdio.h> // for FILE*
+#include <string.h> // for memcpy and bzero
+#include <stdint.h> // for integer typedefs
+
+// Define these macros to hook into a custom memory allocator.
+// TEMP_MALLOC and TEMP_FREE will only be called in stack fashion - frees in the reverse order of mallocs
+// and any temp memory allocated by a function will be freed before it exits.
+// MALLOC and FREE are used only by GifBegin and GifEnd respectively (to allocate a buffer the size of the image, which
+// is used to find changed pixels for delta-encoding.)
+
+#ifndef GIF_TEMP_MALLOC
+#include <stdlib.h>
+#define GIF_TEMP_MALLOC malloc
+#endif
+
+#ifndef GIF_TEMP_FREE
+#include <stdlib.h>
+#define GIF_TEMP_FREE free
+#endif
+
+#ifndef GIF_MALLOC
+#include <stdlib.h>
+#define GIF_MALLOC malloc
+#endif
+
+#ifndef GIF_FREE
+#include <stdlib.h>
+#define GIF_FREE free
+#endif
+
+const int kGifTransIndex = 0;
+
+struct GifPalette
+{
+ int bitDepth;
+
+ uint8_t r[256];
+ uint8_t g[256];
+ uint8_t b[256];
+
+ // k-d tree over RGB space, organized in heap fashion
+ // i.e. left child of node i is node i*2, right child is node i*2+1
+ // nodes 256-511 are implicitly the leaves, containing a color
+ uint8_t treeSplitElt[255];
+ uint8_t treeSplit[255];
+};
+
+// max, min, and abs functions
+int GifIMax(int l, int r) { return l>r?l:r; }
+int GifIMin(int l, int r) { return l<r?l:r; }
+int GifIAbs(int i) { return i<0?-i:i; }
+
+// walks the k-d tree to pick the palette entry for a desired color.
+// Takes as in/out parameters the current best color and its error -
+// only changes them if it finds a better color in its subtree.
+// this is the major hotspot in the code at the moment.
+void GifGetClosestPaletteColor(GifPalette* pPal, int r, int g, int b, int& bestInd, int& bestDiff, int treeRoot = 1)
+{
+ // base case, reached the bottom of the tree
+ if(treeRoot > (1<<pPal->bitDepth)-1)
+ {
+ int ind = treeRoot-(1<<pPal->bitDepth);
+ if(ind == kGifTransIndex) return;
+
+ // check whether this color is better than the current winner
+ int r_err = r - ((int32_t)pPal->r[ind]);
+ int g_err = g - ((int32_t)pPal->g[ind]);
+ int b_err = b - ((int32_t)pPal->b[ind]);
+ int diff = GifIAbs(r_err)+GifIAbs(g_err)+GifIAbs(b_err);
+
+ if(diff < bestDiff)
+ {
+ bestInd = ind;
+ bestDiff = diff;
+ }
+
+ return;
+ }
+
+ // take the appropriate color (r, g, or b) for this node of the k-d tree
+ int comps[3]; comps[0] = r; comps[1] = g; comps[2] = b;
+ int splitComp = comps[pPal->treeSplitElt[treeRoot]];
+
+ int splitPos = pPal->treeSplit[treeRoot];
+ if(splitPos > splitComp)
+ {
+ // check the left subtree
+ GifGetClosestPaletteColor(pPal, r, g, b, bestInd, bestDiff, treeRoot*2);
+ if( bestDiff > splitPos - splitComp )
+ {
+ // cannot prove there's not a better value in the right subtree, check that too
+ GifGetClosestPaletteColor(pPal, r, g, b, bestInd, bestDiff, treeRoot*2+1);
+ }
+ }
+ else
+ {
+ GifGetClosestPaletteColor(pPal, r, g, b, bestInd, bestDiff, treeRoot*2+1);
+ if( bestDiff > splitComp - splitPos )
+ {
+ GifGetClosestPaletteColor(pPal, r, g, b, bestInd, bestDiff, treeRoot*2);
+ }
+ }
+}
+
+void GifSwapPixels(uint8_t* image, int pixA, int pixB)
+{
+ uint8_t rA = image[pixA*4];
+ uint8_t gA = image[pixA*4+1];
+ uint8_t bA = image[pixA*4+2];
+ uint8_t aA = image[pixA*4+3];
+
+ uint8_t rB = image[pixB*4];
+ uint8_t gB = image[pixB*4+1];
+ uint8_t bB = image[pixB*4+2];
+ uint8_t aB = image[pixA*4+3];
+
+ image[pixA*4] = rB;
+ image[pixA*4+1] = gB;
+ image[pixA*4+2] = bB;
+ image[pixA*4+3] = aB;
+
+ image[pixB*4] = rA;
+ image[pixB*4+1] = gA;
+ image[pixB*4+2] = bA;
+ image[pixB*4+3] = aA;
+}
+
+// just the partition operation from quicksort
+int GifPartition(uint8_t* image, const int left, const int right, const int elt, int pivotIndex)
+{
+ const int pivotValue = image[(pivotIndex)*4+elt];
+ GifSwapPixels(image, pivotIndex, right-1);
+ int storeIndex = left;
+ bool split = 0;
+ for(int ii=left; ii<right-1; ++ii)
+ {
+ int arrayVal = image[ii*4+elt];
+ if( arrayVal < pivotValue )
+ {
+ GifSwapPixels(image, ii, storeIndex);
+ ++storeIndex;
+ }
+ else if( arrayVal == pivotValue )
+ {
+ if(split)
+ {
+ GifSwapPixels(image, ii, storeIndex);
+ ++storeIndex;
+ }
+ split = !split;
+ }
+ }
+ GifSwapPixels(image, storeIndex, right-1);
+ return storeIndex;
+}
+
+// Perform an incomplete sort, finding all elements above and below the desired median
+void GifPartitionByMedian(uint8_t* image, int left, int right, int com, int neededCenter)
+{
+ if(left < right-1)
+ {
+ int pivotIndex = left + (right-left)/2;
+
+ pivotIndex = GifPartition(image, left, right, com, pivotIndex);
+
+ // Only "sort" the section of the array that contains the median
+ if(pivotIndex > neededCenter)
+ GifPartitionByMedian(image, left, pivotIndex, com, neededCenter);
+
+ if(pivotIndex < neededCenter)
+ GifPartitionByMedian(image, pivotIndex+1, right, com, neededCenter);
+ }
+}
+
+// Builds a palette by creating a balanced k-d tree of all pixels in the image
+void GifSplitPalette(uint8_t* image, int numPixels, int firstElt, int lastElt, int splitElt, int splitDist, int treeNode, bool buildForDither, GifPalette* pal)
+{
+ if(lastElt <= firstElt || numPixels == 0)
+ return;
+
+ // base case, bottom of the tree
+ if(lastElt == firstElt+1)
+ {
+ if(buildForDither)
+ {
+ // Dithering needs at least one color as dark as anything
+ // in the image and at least one brightest color -
+ // otherwise it builds up error and produces strange artifacts
+ if( firstElt == 1 )
+ {
+ // special case: the darkest color in the image
+ uint32_t r=255, g=255, b=255;
+ for(int ii=0; ii<numPixels; ++ii)
+ {
+ r = (uint32_t)GifIMin((int32_t)r, image[ii * 4 + 0]);
+ g = (uint32_t)GifIMin((int32_t)g, image[ii * 4 + 1]);
+ b = (uint32_t)GifIMin((int32_t)b, image[ii * 4 + 2]);
+ }
+
+ pal->r[firstElt] = (uint8_t)r;
+ pal->g[firstElt] = (uint8_t)g;
+ pal->b[firstElt] = (uint8_t)b;
+
+ return;
+ }
+
+ if( firstElt == (1 << pal->bitDepth)-1 )
+ {
+ // special case: the lightest color in the image
+ uint32_t r=0, g=0, b=0;
+ for(int ii=0; ii<numPixels; ++ii)
+ {
+ r = (uint32_t)GifIMax((int32_t)r, image[ii * 4 + 0]);
+ g = (uint32_t)GifIMax((int32_t)g, image[ii * 4 + 1]);
+ b = (uint32_t)GifIMax((int32_t)b, image[ii * 4 + 2]);
+ }
+
+ pal->r[firstElt] = (uint8_t)r;
+ pal->g[firstElt] = (uint8_t)g;
+ pal->b[firstElt] = (uint8_t)b;
+
+ return;
+ }
+ }
+
+ // otherwise, take the average of all colors in this subcube
+ uint64_t r=0, g=0, b=0;
+ for(int ii=0; ii<numPixels; ++ii)
+ {
+ r += image[ii*4+0];
+ g += image[ii*4+1];
+ b += image[ii*4+2];
+ }
+
+ r += (uint64_t)numPixels / 2; // round to nearest
+ g += (uint64_t)numPixels / 2;
+ b += (uint64_t)numPixels / 2;
+
+ r /= (uint64_t)numPixels;
+ g /= (uint64_t)numPixels;
+ b /= (uint64_t)numPixels;
+
+ pal->r[firstElt] = (uint8_t)r;
+ pal->g[firstElt] = (uint8_t)g;
+ pal->b[firstElt] = (uint8_t)b;
+
+ return;
+ }
+
+ // Find the axis with the largest range
+ int minR = 255, maxR = 0;
+ int minG = 255, maxG = 0;
+ int minB = 255, maxB = 0;
+ for(int ii=0; ii<numPixels; ++ii)
+ {
+ int r = image[ii*4+0];
+ int g = image[ii*4+1];
+ int b = image[ii*4+2];
+
+ if(r > maxR) maxR = r;
+ if(r < minR) minR = r;
+
+ if(g > maxG) maxG = g;
+ if(g < minG) minG = g;
+
+ if(b > maxB) maxB = b;
+ if(b < minB) minB = b;
+ }
+
+ int rRange = maxR - minR;
+ int gRange = maxG - minG;
+ int bRange = maxB - minB;
+
+ // and split along that axis. (incidentally, this means this isn't a "proper" k-d tree but I don't know what else to call it)
+ int splitCom = 1;
+ if(bRange > gRange) splitCom = 2;
+ if(rRange > bRange && rRange > gRange) splitCom = 0;
+
+ int subPixelsA = numPixels * (splitElt - firstElt) / (lastElt - firstElt);
+ int subPixelsB = numPixels-subPixelsA;
+
+ GifPartitionByMedian(image, 0, numPixels, splitCom, subPixelsA);
+
+ pal->treeSplitElt[treeNode] = (uint8_t)splitCom;
+ pal->treeSplit[treeNode] = image[subPixelsA*4+splitCom];
+
+ GifSplitPalette(image, subPixelsA, firstElt, splitElt, splitElt-splitDist, splitDist/2, treeNode*2, buildForDither, pal);
+ GifSplitPalette(image+subPixelsA*4, subPixelsB, splitElt, lastElt, splitElt+splitDist, splitDist/2, treeNode*2+1, buildForDither, pal);
+}
+
+// Finds all pixels that have changed from the previous image and
+// moves them to the fromt of th buffer.
+// This allows us to build a palette optimized for the colors of the
+// changed pixels only.
+int GifPickChangedPixels( const uint8_t* lastFrame, uint8_t* frame, int numPixels )
+{
+ int numChanged = 0;
+ uint8_t* writeIter = frame;
+
+ for (int ii=0; ii<numPixels; ++ii)
+ {
+ if(lastFrame[0] != frame[0] ||
+ lastFrame[1] != frame[1] ||
+ lastFrame[2] != frame[2])
+ {
+ writeIter[0] = frame[0];
+ writeIter[1] = frame[1];
+ writeIter[2] = frame[2];
+ ++numChanged;
+ writeIter += 4;
+ }
+ lastFrame += 4;
+ frame += 4;
+ }
+
+ return numChanged;
+}
+
+// Creates a palette by placing all the image pixels in a k-d tree and then averaging the blocks at the bottom.
+// This is known as the "modified median split" technique
+void GifMakePalette( const uint8_t* lastFrame, const uint8_t* nextFrame, uint32_t width, uint32_t height, int bitDepth, bool buildForDither, GifPalette* pPal )
+{
+ pPal->bitDepth = bitDepth;
+
+ // SplitPalette is destructive (it sorts the pixels by color) so
+ // we must create a copy of the image for it to destroy
+ size_t imageSize = (size_t)(width * height * 4 * sizeof(uint8_t));
+ uint8_t* destroyableImage = (uint8_t*)GIF_TEMP_MALLOC(imageSize);
+ memcpy(destroyableImage, nextFrame, imageSize);
+
+ int numPixels = (int)(width * height);
+ if(lastFrame)
+ numPixels = GifPickChangedPixels(lastFrame, destroyableImage, numPixels);
+
+ const int lastElt = 1 << bitDepth;
+ const int splitElt = lastElt/2;
+ const int splitDist = splitElt/2;
+
+ GifSplitPalette(destroyableImage, numPixels, 1, lastElt, splitElt, splitDist, 1, buildForDither, pPal);
+
+ GIF_TEMP_FREE(destroyableImage);
+
+ // add the bottom node for the transparency index
+ pPal->treeSplit[1 << (bitDepth-1)] = 0;
+ pPal->treeSplitElt[1 << (bitDepth-1)] = 0;
+
+ pPal->r[0] = pPal->g[0] = pPal->b[0] = 0;
+}
+
+// Implements Floyd-Steinberg dithering, writes palette value to alpha
+void GifDitherImage( const uint8_t* lastFrame, const uint8_t* nextFrame, uint8_t* outFrame, uint32_t width, uint32_t height, GifPalette* pPal )
+{
+ int numPixels = (int)(width * height);
+
+ // quantPixels initially holds color*256 for all pixels
+ // The extra 8 bits of precision allow for sub-single-color error values
+ // to be propagated
+ int32_t *quantPixels = (int32_t *)GIF_TEMP_MALLOC(sizeof(int32_t) * (size_t)numPixels * 4);
+
+ for( int ii=0; ii<numPixels*4; ++ii )
+ {
+ uint8_t pix = nextFrame[ii];
+ int32_t pix16 = int32_t(pix) * 256;
+ quantPixels[ii] = pix16;
+ }
+
+ for( uint32_t yy=0; yy<height; ++yy )
+ {
+ for( uint32_t xx=0; xx<width; ++xx )
+ {
+ int32_t* nextPix = quantPixels + 4*(yy*width+xx);
+ const uint8_t* lastPix = lastFrame? lastFrame + 4*(yy*width+xx) : NULL;
+
+ // Compute the colors we want (rounding to nearest)
+ int32_t rr = (nextPix[0] + 127) / 256;
+ int32_t gg = (nextPix[1] + 127) / 256;
+ int32_t bb = (nextPix[2] + 127) / 256;
+
+ // if it happens that we want the color from last frame, then just write out
+ // a transparent pixel
+ if( lastFrame &&
+ lastPix[0] == rr &&
+ lastPix[1] == gg &&
+ lastPix[2] == bb )
+ {
+ nextPix[0] = rr;
+ nextPix[1] = gg;
+ nextPix[2] = bb;
+ nextPix[3] = kGifTransIndex;
+ continue;
+ }
+
+ int32_t bestDiff = 1000000;
+ int32_t bestInd = kGifTransIndex;
+
+ // Search the palete
+ GifGetClosestPaletteColor(pPal, rr, gg, bb, bestInd, bestDiff);
+
+ // Write the result to the temp buffer
+ int32_t r_err = nextPix[0] - int32_t(pPal->r[bestInd]) * 256;
+ int32_t g_err = nextPix[1] - int32_t(pPal->g[bestInd]) * 256;
+ int32_t b_err = nextPix[2] - int32_t(pPal->b[bestInd]) * 256;
+
+ nextPix[0] = pPal->r[bestInd];
+ nextPix[1] = pPal->g[bestInd];
+ nextPix[2] = pPal->b[bestInd];
+ nextPix[3] = bestInd;
+
+ // Propagate the error to the four adjacent locations
+ // that we haven't touched yet
+ int quantloc_7 = (int)(yy * width + xx + 1);
+ int quantloc_3 = (int)(yy * width + width + xx - 1);
+ int quantloc_5 = (int)(yy * width + width + xx);
+ int quantloc_1 = (int)(yy * width + width + xx + 1);
+
+ if(quantloc_7 < numPixels)
+ {
+ int32_t* pix7 = quantPixels+4*quantloc_7;
+ pix7[0] += GifIMax( -pix7[0], r_err * 7 / 16 );
+ pix7[1] += GifIMax( -pix7[1], g_err * 7 / 16 );
+ pix7[2] += GifIMax( -pix7[2], b_err * 7 / 16 );
+ }
+
+ if(quantloc_3 < numPixels)
+ {
+ int32_t* pix3 = quantPixels+4*quantloc_3;
+ pix3[0] += GifIMax( -pix3[0], r_err * 3 / 16 );
+ pix3[1] += GifIMax( -pix3[1], g_err * 3 / 16 );
+ pix3[2] += GifIMax( -pix3[2], b_err * 3 / 16 );
+ }
+
+ if(quantloc_5 < numPixels)
+ {
+ int32_t* pix5 = quantPixels+4*quantloc_5;
+ pix5[0] += GifIMax( -pix5[0], r_err * 5 / 16 );
+ pix5[1] += GifIMax( -pix5[1], g_err * 5 / 16 );
+ pix5[2] += GifIMax( -pix5[2], b_err * 5 / 16 );
+ }
+
+ if(quantloc_1 < numPixels)
+ {
+ int32_t* pix1 = quantPixels+4*quantloc_1;
+ pix1[0] += GifIMax( -pix1[0], r_err / 16 );
+ pix1[1] += GifIMax( -pix1[1], g_err / 16 );
+ pix1[2] += GifIMax( -pix1[2], b_err / 16 );
+ }
+ }
+ }
+
+ // Copy the palettized result to the output buffer
+ for( int ii=0; ii<numPixels*4; ++ii )
+ {
+ outFrame[ii] = (uint8_t)quantPixels[ii];
+ }
+
+ GIF_TEMP_FREE(quantPixels);
+}
+
+// Picks palette colors for the image using simple thresholding, no dithering
+void GifThresholdImage( const uint8_t* lastFrame, const uint8_t* nextFrame, uint8_t* outFrame, uint32_t width, uint32_t height, GifPalette* pPal )
+{
+ uint32_t numPixels = width*height;
+ for( uint32_t ii=0; ii<numPixels; ++ii )
+ {
+ // if a previous color is available, and it matches the current color,
+ // set the pixel to transparent
+ if(lastFrame &&
+ lastFrame[0] == nextFrame[0] &&
+ lastFrame[1] == nextFrame[1] &&
+ lastFrame[2] == nextFrame[2])
+ {
+ outFrame[0] = lastFrame[0];
+ outFrame[1] = lastFrame[1];
+ outFrame[2] = lastFrame[2];
+ outFrame[3] = kGifTransIndex;
+ }
+ else
+ {
+ // palettize the pixel
+ int32_t bestDiff = 1000000;
+ int32_t bestInd = 1;
+ GifGetClosestPaletteColor(pPal, nextFrame[0], nextFrame[1], nextFrame[2], bestInd, bestDiff);
+
+ // Write the resulting color to the output buffer
+ outFrame[0] = pPal->r[bestInd];
+ outFrame[1] = pPal->g[bestInd];
+ outFrame[2] = pPal->b[bestInd];
+ outFrame[3] = (uint8_t)bestInd;
+ }
+
+ if(lastFrame) lastFrame += 4;
+ outFrame += 4;
+ nextFrame += 4;
+ }
+}
+
+// Simple structure to write out the LZW-compressed portion of the image
+// one bit at a time
+struct GifBitStatus
+{
+ uint8_t bitIndex; // how many bits in the partial byte written so far
+ uint8_t byte; // current partial byte
+
+ uint32_t chunkIndex;
+ uint8_t chunk[256]; // bytes are written in here until we have 256 of them, then written to the file
+};
+
+// insert a single bit
+void GifWriteBit( GifBitStatus& stat, uint32_t bit )
+{
+ bit = bit & 1;
+ bit = bit << stat.bitIndex;
+ stat.byte |= bit;
+
+ ++stat.bitIndex;
+ if( stat.bitIndex > 7 )
+ {
+ // move the newly-finished byte to the chunk buffer
+ stat.chunk[stat.chunkIndex++] = stat.byte;
+ // and start a new byte
+ stat.bitIndex = 0;
+ stat.byte = 0;
+ }
+}
+
+// write all bytes so far to the file
+void GifWriteChunk( FILE* f, GifBitStatus& stat )
+{
+ fputc((int)stat.chunkIndex, f);
+ fwrite(stat.chunk, 1, stat.chunkIndex, f);
+
+ stat.bitIndex = 0;
+ stat.byte = 0;
+ stat.chunkIndex = 0;
+}
+
+void GifWriteCode( FILE* f, GifBitStatus& stat, uint32_t code, uint32_t length )
+{
+ for( uint32_t ii=0; ii<length; ++ii )
+ {
+ GifWriteBit(stat, code);
+ code = code >> 1;
+
+ if( stat.chunkIndex == 255 )
+ {
+ GifWriteChunk(f, stat);
+ }
+ }
+}
+
+// The LZW dictionary is a 256-ary tree constructed as the file is encoded,
+// this is one node
+struct GifLzwNode
+{
+ uint16_t m_next[256];
+};
+
+// write a 256-color (8-bit) image palette to the file
+void GifWritePalette( const GifPalette* pPal, FILE* f )
+{
+ fputc(0, f); // first color: transparency
+ fputc(0, f);
+ fputc(0, f);
+
+ for(int ii=1; ii<(1 << pPal->bitDepth); ++ii)
+ {
+ uint32_t r = pPal->r[ii];
+ uint32_t g = pPal->g[ii];
+ uint32_t b = pPal->b[ii];
+
+ fputc((int)r, f);
+ fputc((int)g, f);
+ fputc((int)b, f);
+ }
+}
+
+// write the image header, LZW-compress and write out the image
+void GifWriteLzwImage(FILE* f, uint8_t* image, uint32_t left, uint32_t top, uint32_t width, uint32_t height, uint32_t delay, GifPalette* pPal)
+{
+ // graphics control extension
+ fputc(0x21, f);
+ fputc(0xf9, f);
+ fputc(0x04, f);
+ fputc(0x05, f); // leave prev frame in place, this frame has transparency
+ fputc(delay & 0xff, f);
+ fputc((delay >> 8) & 0xff, f);
+ fputc(kGifTransIndex, f); // transparent color index
+ fputc(0, f);
+
+ fputc(0x2c, f); // image descriptor block
+
+ fputc(left & 0xff, f); // corner of image in canvas space
+ fputc((left >> 8) & 0xff, f);
+ fputc(top & 0xff, f);
+ fputc((top >> 8) & 0xff, f);
+
+ fputc(width & 0xff, f); // width and height of image
+ fputc((width >> 8) & 0xff, f);
+ fputc(height & 0xff, f);
+ fputc((height >> 8) & 0xff, f);
+
+ //fputc(0, f); // no local color table, no transparency
+ //fputc(0x80, f); // no local color table, but transparency
+
+ fputc(0x80 + pPal->bitDepth-1, f); // local color table present, 2 ^ bitDepth entries
+ GifWritePalette(pPal, f);
+
+ const int minCodeSize = pPal->bitDepth;
+ const uint32_t clearCode = 1 << pPal->bitDepth;
+
+ fputc(minCodeSize, f); // min code size 8 bits
+
+ GifLzwNode* codetree = (GifLzwNode*)GIF_TEMP_MALLOC(sizeof(GifLzwNode)*4096);
+
+ memset(codetree, 0, sizeof(GifLzwNode)*4096);
+ int32_t curCode = -1;
+ uint32_t codeSize = (uint32_t)minCodeSize + 1;
+ uint32_t maxCode = clearCode+1;
+
+ GifBitStatus stat;
+ stat.byte = 0;
+ stat.bitIndex = 0;
+ stat.chunkIndex = 0;
+
+ GifWriteCode(f, stat, clearCode, codeSize); // start with a fresh LZW dictionary
+
+ for(uint32_t yy=0; yy<height; ++yy)
+ {
+ for(uint32_t xx=0; xx<width; ++xx)
+ {
+ #ifdef GIF_FLIP_VERT
+ // bottom-left origin image (such as an OpenGL capture)
+ uint8_t nextValue = image[((height-1-yy)*width+xx)*4+3];
+ #else
+ // top-left origin
+ uint8_t nextValue = image[(yy*width+xx)*4+3];
+ #endif
+
+ // "loser mode" - no compression, every single code is followed immediately by a clear
+ //WriteCode( f, stat, nextValue, codeSize );
+ //WriteCode( f, stat, 256, codeSize );
+
+ if( curCode < 0 )
+ {
+ // first value in a new run
+ curCode = nextValue;
+ }
+ else if( codetree[curCode].m_next[nextValue] )
+ {
+ // current run already in the dictionary
+ curCode = codetree[curCode].m_next[nextValue];
+ }
+ else
+ {
+ // finish the current run, write a code
+ GifWriteCode(f, stat, (uint32_t)curCode, codeSize);
+
+ // insert the new run into the dictionary
+ codetree[curCode].m_next[nextValue] = (uint16_t)++maxCode;
+
+ if( maxCode >= (1ul << codeSize) )
+ {
+ // dictionary entry count has broken a size barrier,
+ // we need more bits for codes
+ codeSize++;
+ }
+ if( maxCode == 4095 )
+ {
+ // the dictionary is full, clear it out and begin anew
+ GifWriteCode(f, stat, clearCode, codeSize); // clear tree
+
+ memset(codetree, 0, sizeof(GifLzwNode)*4096);
+ codeSize = (uint32_t)(minCodeSize + 1);
+ maxCode = clearCode+1;
+ }
+
+ curCode = nextValue;
+ }
+ }
+ }
+
+ // compression footer
+ GifWriteCode(f, stat, (uint32_t)curCode, codeSize);
+ GifWriteCode(f, stat, clearCode, codeSize);
+ GifWriteCode(f, stat, clearCode + 1, (uint32_t)minCodeSize + 1);
+
+ // write out the last partial chunk
+ while( stat.bitIndex ) GifWriteBit(stat, 0);
+ if( stat.chunkIndex ) GifWriteChunk(f, stat);
+
+ fputc(0, f); // image block terminator
+
+ GIF_TEMP_FREE(codetree);
+}
+
+struct GifWriter
+{
+ FILE* f;
+ uint8_t* oldImage;
+ bool firstFrame;
+};
+
+// Creates a gif file.
+// The input GIFWriter is assumed to be uninitialized.
+// The delay value is the time between frames in hundredths of a second - note that not all viewers pay much attention to this value.
+bool GifBegin( GifWriter* writer, const char* filename, uint32_t width, uint32_t height, uint32_t delay, int32_t bitDepth = 8, bool dither = false )
+{
+ (void)bitDepth; (void)dither; // Mute "Unused argument" warnings
+#if defined(_MSC_VER) && (_MSC_VER >= 1400)
+ writer->f = 0;
+ fopen_s(&writer->f, filename, "wb");
+#else
+ writer->f = fopen(filename, "wb");
+#endif
+ if(!writer->f) return false;
+
+ writer->firstFrame = true;
+
+ // allocate
+ writer->oldImage = (uint8_t*)GIF_MALLOC(width*height*4);
+
+ fputs("GIF89a", writer->f);
+
+ // screen descriptor
+ fputc(width & 0xff, writer->f);
+ fputc((width >> 8) & 0xff, writer->f);
+ fputc(height & 0xff, writer->f);
+ fputc((height >> 8) & 0xff, writer->f);
+
+ fputc(0xf0, writer->f); // there is an unsorted global color table of 2 entries
+ fputc(0, writer->f); // background color
+ fputc(0, writer->f); // pixels are square (we need to specify this because it's 1989)
+
+ // now the "global" palette (really just a dummy palette)
+ // color 0: black
+ fputc(0, writer->f);
+ fputc(0, writer->f);
+ fputc(0, writer->f);
+ // color 1: also black
+ fputc(0, writer->f);
+ fputc(0, writer->f);
+ fputc(0, writer->f);
+
+ if( delay != 0 )
+ {
+ // animation header
+ fputc(0x21, writer->f); // extension
+ fputc(0xff, writer->f); // application specific
+ fputc(11, writer->f); // length 11
+ fputs("NETSCAPE2.0", writer->f); // yes, really
+ fputc(3, writer->f); // 3 bytes of NETSCAPE2.0 data
+
+ fputc(1, writer->f); // JUST BECAUSE
+ fputc(0, writer->f); // loop infinitely (byte 0)
+ fputc(0, writer->f); // loop infinitely (byte 1)
+
+ fputc(0, writer->f); // block terminator
+ }
+
+ return true;
+}
+
+// Writes out a new frame to a GIF in progress.
+// The GIFWriter should have been created by GIFBegin.
+// AFAIK, it is legal to use different bit depths for different frames of an image -
+// this may be handy to save bits in animations that don't change much.
+bool GifWriteFrame( GifWriter* writer, const uint8_t* image, uint32_t width, uint32_t height, uint32_t delay, int bitDepth = 8, bool dither = false )
+{
+ if(!writer->f) return false;
+
+ const uint8_t* oldImage = writer->firstFrame? NULL : writer->oldImage;
+ writer->firstFrame = false;
+
+ GifPalette pal;
+ GifMakePalette((dither? NULL : oldImage), image, width, height, bitDepth, dither, &pal);
+
+ if(dither)
+ GifDitherImage(oldImage, image, writer->oldImage, width, height, &pal);
+ else
+ GifThresholdImage(oldImage, image, writer->oldImage, width, height, &pal);
+
+ GifWriteLzwImage(writer->f, writer->oldImage, 0, 0, width, height, delay, &pal);
+
+ return true;
+}
+
+// Writes the EOF code, closes the file handle, and frees temp memory used by a GIF.
+// Many if not most viewers will still display a GIF properly if the EOF code is missing,
+// but it's still a good idea to write it out.
+bool GifEnd( GifWriter* writer )
+{
+ if(!writer->f) return false;
+
+ fputc(0x3b, writer->f); // end of file
+ fclose(writer->f);
+ GIF_FREE(writer->oldImage);
+
+ writer->f = NULL;
+ writer->oldImage = NULL;
+
+ return true;
+}
+
+#endif
projects / platform / core / uifw / lottie-player.git / commitdiff