add test for zero compression

tests/avoid_compression.c

@@ -0,0 +1,74 @@
+#include <stdlib.h>
+#include <stdint.h>
+#include <string.h>
+#include <stdio.h>
+
+#include "cgif.h"
+
+#define WIDTH 3840  // 4096 - 2 - 256 = 3838 (free lzw codes)  +1 (to force dict reset: k pixels make adding k-1 codes)  +1 to overflow if too litte is allocated in pLZWData
+#define HEIGHT 1
+
+static uint64_t seed;
+
+int psdrand(void) {
+  // simple pseudo random function from musl libc
+  seed = 6364136223846793005ULL * seed + 1;
+  return seed >> 33;
+}
+
+int main(void) {
+  CGIF*          pGIF;
+  CGIF_Config     gConfig;
+  CGIF_FrameConfig   fConfig;
+  uint8_t*      pImageData;
+  cgif_result   r;
+  int palette_size = 256;
+  uint8_t       aPalette[palette_size * 3]; 
+
+  seed = 42;
+  for(int i = 0; i < palette_size; ++i) {
+    aPalette[i * 3]     = psdrand() % 256;
+    aPalette[i * 3 + 1] = psdrand() % 256;
+    aPalette[i * 3 + 2] = psdrand() % 256;
+  }
+  memset(&gConfig, 0, sizeof(CGIF_Config));
+  memset(&fConfig, 0, sizeof(CGIF_FrameConfig));
+  gConfig.width                   = WIDTH;
+  gConfig.height                  = HEIGHT;
+  gConfig.pGlobalPalette          = aPalette;
+  gConfig.numGlobalPaletteEntries = palette_size;
+  gConfig.path                    = "avoid_compression.gif";
+  //
+  // create new GIF
+  pGIF = cgif_newgif(&gConfig);
+  if(pGIF == NULL) {
+    fputs("failed to create new GIF via cgif_newgif()\n", stderr);
+    return 1;
+  }
+  //
+  // add frames to GIF
+  uint8_t* code_dict = malloc(sizeof(uint8_t)*palette_size*palette_size); // to check if codes are used already, then avoid them
+  memset(code_dict, 0, sizeof(uint8_t)*palette_size*palette_size);
+  pImageData = malloc(WIDTH * HEIGHT);
+  pImageData[0] = psdrand() % palette_size;
+  for(int i = 1; i < WIDTH * HEIGHT; ++i){
+    uint8_t idx = 0;
+    while (idx == 0 || code_dict[palette_size*idx + pImageData[i-1]]) idx = psdrand() % palette_size;
+    pImageData[i] = idx;
+	code_dict[palette_size*idx + pImageData[i-1]] = 1;  //mark code as used
+  }
+  fConfig.pImageData = pImageData;
+  r = cgif_addframe(pGIF, &fConfig);
+  free(code_dict);
+  free(pImageData);
+  //
+  // write GIF to file
+  r = cgif_close(pGIF); // free allocated space at the end of the session
+
+  // check for errors
+  if(r != CGIF_OK) {
+    fprintf(stderr, "failed to create GIF. error code: %d\n", r);
+    return 2;
+  }
+  return 0;
+}

tests/meson.build

@@ -12,6 +12,7 @@ tests_index = [
   { 'name' : 'animated_snake',                     'seed_should_fail' : false},
   { 'name' : 'animated_stripes_horizontal',        'seed_should_fail' : false},
   { 'name' : 'animated_stripe_pattern',            'seed_should_fail' : false},
+  { 'name' : 'avoid_compression',                  'seed_should_fail' : false},
   { 'name' : 'animated_stripe_pattern_2',          'seed_should_fail' : false},
   { 'name' : 'duplicate_frames',                   'seed_should_fail' : false},
   { 'name' : 'earlyclose',                         'seed_should_fail' : true },