Merge pull request #48 from dloebl/no-loop

Allow creating GIF animations with no repetitions

README.md

@@ -36,6 +36,7 @@ With our encoder you can create animated or static GIFs, you can or cannot use c
 CGIF_ATTR_IS_ANIMATED              // make an animated GIF (default is non-animated GIF)
 CGIF_ATTR_NO_GLOBAL_TABLE          // disable global color table (global color table is default)
 CGIF_ATTR_HAS_TRANSPARENCY         // first entry in color table contains transparency (alpha channel)
+CGIF_ATTR_NO_LOOP                  // run GIF animation only one time. numLoops is ignored (no repetitions)
 CGIF_FRAME_ATTR_USE_LOCAL_TABLE    // use a local color table for a frame (not used by default)
 CGIF_FRAME_ATTR_HAS_ALPHA          // frame contains alpha channel (index set via transIndex field)
 CGIF_FRAME_ATTR_HAS_SET_TRANS      // transparency setting provided by user (transIndex field)

inc/cgif.h

@@ -12,6 +12,7 @@ extern "C" {
 #define CGIF_ATTR_IS_ANIMATED            (1uL << 1)       // make an animated GIF (default is non-animated GIF)
 #define CGIF_ATTR_NO_GLOBAL_TABLE        (1uL << 2)       // disable global color table (global color table is default)
 #define CGIF_ATTR_HAS_TRANSPARENCY       (1uL << 3)       // first entry in color table contains transparency (alpha channel)
+#define CGIF_ATTR_NO_LOOP                (1uL << 4)       // don't loop a GIF animation: only play it one time.
 #define CGIF_FRAME_ATTR_USE_LOCAL_TABLE  (1uL << 0)       // use a local color table for a frame (local color table is not used by default)
 #define CGIF_FRAME_ATTR_HAS_ALPHA        (1uL << 1)       // alpha channel index provided by user (transIndex field)
 #define CGIF_FRAME_ATTR_HAS_SET_TRANS    (1uL << 2)       // transparency setting provided by user (transIndex field)

inc/cgif_raw.h

@@ -15,6 +15,7 @@ extern "C" {
 
 // flags to set the GIF attributes
 #define CGIF_RAW_ATTR_IS_ANIMATED     (1uL << 0) // make an animated GIF (default is non-animated GIF)
+#define CGIF_RAW_ATTR_NO_LOOP         (1uL << 1) // don't loop a GIF animation: only play it one time.
 
 // flags to set the Frame attributes
 #define CGIF_RAW_FRAME_ATTR_HAS_TRANS (1uL << 0) // provided transIndex should be set
@@ -29,7 +30,7 @@ typedef struct {
   uint16_t       width;        // effective width of each frame in the GIF
   uint16_t       height;       // effective height of each frame in the GIF
   uint16_t       sizeGCT;      // size of the global color table (GCT)
-  uint16_t       numLoops;     // number of repetitons of an animated GIF (set to INFINITE_LOOP for infinite loop)
+  uint16_t       numLoops;     // number of repetitons of an animated GIF (set to INFINITE_LOOP resp. 0 for infinite loop, use CGIF_ATTR_NO_LOOP if you don't want any repetition)
 } CGIFRaw_Config;
 
 // CGIFRaw_FrameConfig type

meson.build

@@ -1,7 +1,7 @@
 project(
   'libcgif',
   'c',
-  version : '0.2.1',
+  version : '0.3.0',
   license : 'MIT',
   default_options : ['c_std=c99'],
 )
@@ -12,7 +12,7 @@ lib = library(
   cgif_sources,
   include_directories : ['inc/'],
   soversion : '0',
-  version : '0.2.1',
+  version : '0.3.0',
   install : true,
 )
 

src/cgif.c

@@ -104,6 +104,7 @@ CGIF* cgif_newgif(CGIF_Config* pConfig) {
   rawConfig.sizeGCT   = (pConfig->attrFlags & CGIF_ATTR_NO_GLOBAL_TABLE) ? 0 : pConfig->numGlobalPaletteEntries;
   // translate CGIF_ATTR_* to CGIF_RAW_ATTR_* flags
   rawConfig.attrFlags = (pConfig->attrFlags & CGIF_ATTR_IS_ANIMATED) ? CGIF_RAW_ATTR_IS_ANIMATED : 0;
+  rawConfig.attrFlags |= (pConfig->attrFlags & CGIF_ATTR_NO_LOOP) ? CGIF_RAW_ATTR_NO_LOOP : 0;
   rawConfig.width     = pConfig->width;
   rawConfig.height    = pConfig->height;
   rawConfig.numLoops  = pConfig->numLoops;

src/cgif_raw.c

@@ -449,7 +449,8 @@ CGIFRaw* cgif_raw_newgif(const CGIFRaw_Config* pConfig) {
     rWrite |= writeDummyBytes(pConfig->pWriteFn, pConfig->pContext, numBytesLeft);
   }
   // GIF should be animated? => init & write app extension header ("NETSCAPE2.0")
-  if(pConfig->attrFlags & CGIF_RAW_ATTR_IS_ANIMATED) {
+  // No loop? Don't write NETSCAPE extension.
+  if((pConfig->attrFlags & CGIF_RAW_ATTR_IS_ANIMATED) && !(pConfig->attrFlags & CGIF_RAW_ATTR_NO_LOOP)) {
     initAppExtBlock(aAppExt, pConfig->numLoops);
     rWrite |= pConfig->pWriteFn(pConfig->pContext, aAppExt, SIZE_APP_EXT);
   }

tests/meson.build

@@ -22,6 +22,7 @@ tests = [
   'more_than_256_colors',
   'noise256',
   'noise6',
+  'noloop',
   'one_full_block',
   'only_local_table',
   'overlap_everything',

tests/noloop.c

@@ -0,0 +1,71 @@
+#include <stdlib.h>
+#include <stdint.h>
+#include <time.h>
+#include <string.h>
+#include <stdio.h>
+
+#include "cgif.h"
+
+#define WIDTH  50
+#define HEIGHT 50
+
+static void initGIFConfig(CGIF_Config* pConfig, uint8_t* pGlobalPalette, uint16_t numColors, uint32_t attrFlags, uint16_t width, uint16_t height) {
+  memset(pConfig, 0, sizeof(CGIF_Config));
+  pConfig->attrFlags               = attrFlags;
+  pConfig->width                   = width;
+  pConfig->height                  = height;
+  pConfig->pGlobalPalette          = pGlobalPalette;
+  pConfig->numGlobalPaletteEntries = numColors;
+  pConfig->path                    = "noloop.gif";
+}
+
+static void initFrameConfig(CGIF_FrameConfig* pConfig, uint8_t* pImageData, uint16_t delay, uint32_t genFlags) {
+  memset(pConfig, 0, sizeof(CGIF_FrameConfig));
+  pConfig->pImageData = pImageData;
+  pConfig->delay      = delay;
+  pConfig->genFlags   = genFlags;
+}
+
+int main(void) {
+  CGIF*          pGIF;
+  CGIF_Config      gConfig;
+  CGIF_FrameConfig    fConfig;
+  uint8_t*      pImageData;
+  uint8_t aPalette[] = {
+    0xFF, 0xFF, 0xFF, // white
+    0xFF, 0x00, 0x00, // red
+    0x00, 0xFF, 0x00, // green
+  };
+  cgif_result r;
+  const uint16_t numColors = 3;   // number of colors in aPalette
+  //
+  // create new GIF
+  initGIFConfig(&gConfig, aPalette, numColors, CGIF_ATTR_IS_ANIMATED | CGIF_ATTR_NO_LOOP, WIDTH, HEIGHT);
+  pGIF = cgif_newgif(&gConfig);
+  if(pGIF == NULL) {
+    fputs("failed to create new GIF via cgif_newgif()\n", stderr);
+    return 1;
+  }
+  //
+  // add frames to GIF
+  pImageData = malloc(WIDTH * HEIGHT); // Actual image data
+  memset(pImageData, 0, WIDTH * HEIGHT);
+  initFrameConfig(&fConfig, pImageData, 50, CGIF_FRAME_GEN_USE_TRANSPARENCY | CGIF_FRAME_GEN_USE_DIFF_WINDOW);
+  r = cgif_addframe(pGIF, &fConfig); // append the new frame
+  memset(pImageData, 1, WIDTH * HEIGHT);
+  r = cgif_addframe(pGIF, &fConfig); // append the next frame
+  memset(pImageData, 2, WIDTH * HEIGHT);
+  r = cgif_addframe(pGIF, &fConfig); // append the next frame
+  //
+  free(pImageData);
+  //
+  // Free allocated space at the end of the session
+  r = cgif_close(pGIF);
+
+  // check for errors
+  if(r != CGIF_OK) {
+    fprintf(stderr, "failed to create GIF. error code: %d\n", r);
+    return 2;
+  }
+  return 0;
+}

tests/tests.md5

@@ -18,6 +18,7 @@ f2bfeb47a7ecc834ae21140f02c60297  min_size.gif
 bcf6674e99f31e67da5bc17ad93cb7a7  more_than_256_colors.gif
 c6a8e6f6d6d0c969cb300ea7eb18391d  noise256.gif
 7de24bdbff1dec81aab1840bcf69b19f  noise6.gif
+92336ea86024feb0a65bc21fde9bee61  noloop.gif
 3337de21095a6b19effb40c518af96e5  one_full_block.gif
 a7c04cb7b6d19a16023497da03384408  only_local_table.gif
 013513307101f1d6b80164cdb3318c1c  overlap_everything.gif