webpdec.h: single-file WebP decoder

libwebp 1.6.0's decode + demux path (lossy VP8, lossless VP8L, VP8X container, ALPH alpha, and the WebPDemux/WebPAnimDecoder animation API) amalgamated into one stb-style header, built as portable C99 with all SIMD, threads and host file I/O disabled. amalgamate.py regenerates webpdec.h from a pinned, auto-cloned libwebp checkout; tests/run.sh checks decode output bit-exactly against reference libwebp. Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
2026-06-14 03:28:11 +00:00
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+/* exercises the demux + animation API folded into the single header */
+#include <stdio.h>
+#include <stdlib.h>
+
+#define WEBPDEC_IMPLEMENTATION
+#include "webpdec.h"
+
+static unsigned char* slurp(const char* p, size_t* n){
+  FILE* f=fopen(p,"rb"); if(!f) return 0;
+  fseek(f,0,SEEK_END); long L=ftell(f); fseek(f,0,SEEK_SET);
+  unsigned char* b=malloc(L); if(fread(b,1,L,f)!=(size_t)L){} fclose(f); *n=L; return b;
+}
+
+int main(int argc,char**argv){
+  size_t n; unsigned char* buf=slurp(argv[1],&n);
+  if(!buf){ printf("no file\n"); return 1; }
+
+  WebPData data = { buf, n };
+
+  /* --- demux: report canvas + frame/loop count --- */
+  WebPDemuxer* dmux = WebPDemux(&data);
+  if(!dmux){ printf("WebPDemux failed\n"); return 1; }
+  unsigned cw = WebPDemuxGetI(dmux, WEBP_FF_CANVAS_WIDTH);
+  unsigned ch = WebPDemuxGetI(dmux, WEBP_FF_CANVAS_HEIGHT);
+  unsigned nf = WebPDemuxGetI(dmux, WEBP_FF_FRAME_COUNT);
+  unsigned lp = WebPDemuxGetI(dmux, WEBP_FF_LOOP_COUNT);
+  unsigned fl = WebPDemuxGetI(dmux, WEBP_FF_FORMAT_FLAGS);
+  printf("demux: canvas=%ux%u frames=%u loop=%u flags=0x%x\n", cw,ch,nf,lp,fl);
+  WebPDemuxDelete(dmux);
+
+  /* --- animation: decode every frame via WebPAnimDecoder --- */
+  WebPAnimDecoderOptions opt;
+  WebPAnimDecoderOptionsInit(&opt);
+  opt.color_mode = MODE_RGBA;
+  WebPAnimDecoder* adec = WebPAnimDecoderNew(&data, &opt);
+  if(!adec){ printf("WebPAnimDecoderNew failed\n"); return 1; }
+  WebPAnimInfo info;
+  WebPAnimDecoderGetInfo(adec, &info);
+  printf("anim: %ux%u frames=%u loops=%u bgcolor=0x%08x\n",
+         info.canvas_width, info.canvas_height, info.frame_count,
+         info.loop_count, info.bgcolor);
+  int prev = 0, got = 0;
+  while (WebPAnimDecoderHasMoreFrames(adec)) {
+    uint8_t* frgba; int ts;
+    if (!WebPAnimDecoderGetNext(adec, &frgba, &ts)) { printf("GetNext failed\n"); break; }
+    long c = ((long)info.canvas_height/2*info.canvas_width + info.canvas_width/2)*4;
+    printf("  frame %d  ts=%dms (+%dms)  centerRGBA=%d,%d,%d,%d\n",
+           got, ts, ts-prev, frgba[c],frgba[c+1],frgba[c+2],frgba[c+3]);
+    prev = ts; got++;
+  }
+  printf("decoded %d/%u frames -> %s\n", got, info.frame_count,
+         (got==(int)info.frame_count)?"OK":"MISMATCH");
+  WebPAnimDecoderDelete(adec);
+  free(buf);
+  return 0;
+}