progress with gif encoder transparency

EyalAr · Dec 10, 2014 · 331770b · 331770b
1 parent b4dcfbf
commit 331770b
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Showing 4 changed files with 54 additions and 9 deletions.
diff --git a/gifdemo.js b/gifdemo.js
@@ -1,7 +1,7 @@
 var lwip = require('./'), i;
-lwip.open('examples/lena.jpg',function(err, image){
+lwip.open('tests/images/trans.png',function(err, image){
     if (err) return console.log(err);
-    image.writeFile('examples/lena_e.gif',{colors:5, interlaced: true, transparency: false},function(err){
+    image.writeFile('trans.gif',{colors:256, interlaced: false, transparency: true},function(err){
         if (err) console.log(err);
     });
 });
diff --git a/lib/util.js b/lib/util.js
@@ -74,7 +74,8 @@
         params.interlaced = params.interlaced || defs.defaults.PNG_DEF_INTERLACED;
         if (typeof params.interlaced !== 'boolean')
             throw Error('PNG \'interlaced\' must be boolean');
-        params.transparency = params.transparency || defs.defaults.PNG_DEF_TRANSPARENT;
+        if (params.transparency !== false)
+            params.transparency = params.transparency || defs.defaults.PNG_DEF_TRANSPARENT;
         if (typeof params.transparency !== 'boolean'){
             if (typeof params.transparency !== 'string' ||
                 params.transparency.toLowerCase() !== 'auto')
@@ -89,7 +90,8 @@
         params.interlaced = params.interlaced || defs.defaults.GIF_DEF_INTERLACED;
         if (typeof params.interlaced !== 'boolean')
             throw Error('GIF \'interlaced\' must be boolean');
-        params.transparency = params.transparency || defs.defaults.GIF_DEF_TRANSPARENT;
+        if (params.transparency !== false)
+            params.transparency = params.transparency || defs.defaults.GIF_DEF_TRANSPARENT;
         if (typeof params.transparency !== 'boolean'){
             if (typeof params.transparency !== 'string' ||
                 params.transparency.toLowerCase() !== 'auto')

diff --git a/src/encoder/encoder.h b/src/encoder/encoder.h
@@ -121,6 +121,7 @@ NAN_METHOD(encodeToPngBuffer);
 NAN_METHOD(encodeToGifBuffer);
 void pngWriteCB(png_structp png_ptr, png_bytep data, png_size_t length);
 int gifWriteCB(GifFileType * gif, const GifByteType * chunk, int len);
+void remapTransparentPixels(unsigned char * target, const unsigned char * map, size_t width, size_t height, int transColor, int threshold);
 void initAll(Handle<Object> exports);
 
 #endif
diff --git a/src/encoder/gif_worker.cpp b/src/encoder/gif_worker.cpp
@@ -17,18 +17,25 @@ EncodeToGifBufferWorker::EncodeToGifBufferWorker(
     _gifbuf(NULL), _gifbufsize(0) {
     SaveToPersistent("buff", buff); // make sure buff isn't GC'ed
     _pixbuf = (unsigned char *) Buffer::Data(buff);
+    if (_trans){
+        // make room in the color table for a transparent color
+        if (_cmapSize == 256){
+            if (_colors == 256) _colors--;
+        } else if (_cmapSize == _colors){
+            _cmapSize *= 2;
+        }
+    }
 }
 
 EncodeToGifBufferWorker::~EncodeToGifBufferWorker() {}
 
 void EncodeToGifBufferWorker::Execute () {
 
-    (void) _trans; // supress compiler warning TODO: remove
-
     GifByteType
         * redBuff = (GifByteType *) _pixbuf,
         * greenBuff = (GifByteType *) _pixbuf + _width * _height,
         * blueBuff = (GifByteType *) _pixbuf + 2 * _width * _height,
+        * alphaBuff = (GifByteType *) _pixbuf + 3 * _width * _height,
         * gifimgbuf = (GifByteType *) malloc(_width * _height * sizeof(GifByteType)); // the indexed image
     ColorMapObject *cmap;
     SavedImage * simg;
@@ -56,6 +63,7 @@ void EncodeToGifBufferWorker::Execute () {
         SetErrorMessage("Unable to quantize image");
         return;
     }
+    cmap->ColorCount = _colors;
 
     int errcode;
     gifWriteCbData buffinf = {NULL, 0};
@@ -72,9 +80,6 @@ void EncodeToGifBufferWorker::Execute () {
 
     gif->SWidth = _width;
     gif->SHeight = _height;
-    gif->SColorResolution = _colors;
-    gif->SBackGroundColor = 0;
-    gif->SColorMap = cmap;
 
     simg = GifMakeSavedImage(gif, NULL);
 
@@ -90,8 +95,35 @@ void EncodeToGifBufferWorker::Execute () {
     simg->ImageDesc.Width = _width;
     simg->ImageDesc.Height = _height;
     simg->ImageDesc.Interlace = _interlaced;
+    simg->ImageDesc.ColorMap = cmap;
     simg->RasterBits = gifimgbuf;
 
+    printf("extblockcount %d\n", simg->ExtensionBlockCount);
+
+    // transperancy
+    if (_trans){
+        printf("yes, trans\n");
+        ExtensionBlock ext;
+        // 1. assign transparent color index in color table
+        GraphicsControlBlock gcb = {0, false, 0, _colors++};
+        // 2. replace transparent pixels above threshold with this color
+        remapTransparentPixels(gifimgbuf, alphaBuff, _width, _height, gcb.TransparentColor, 50);
+        // gif->SBackGroundColor = gcb.TransparentColor;
+        // 3. create a control block
+        size_t extlen = EGifGCBToExtension(&gcb, (GifByteType *) &ext);
+        if (GIF_ERROR == GifAddExtensionBlock(
+                &(gif->ExtensionBlockCount),
+                &(gif->ExtensionBlocks),
+                GRAPHICS_EXT_FUNC_CODE,
+                extlen,
+                (unsigned char *) &ext)
+            ) {
+            EGifCloseFile(gif, &errcode);
+            SetErrorMessage("Out of memory");
+            return;
+        }
+    }
+
     if (GIF_ERROR == EGifSpew(gif)){
         EGifCloseFile(gif, &errcode);
         SetErrorMessage(GifErrorString(gif->Error));
@@ -132,3 +164,13 @@ int gifWriteCB(GifFileType * gif, const GifByteType * chunk, int len) {
 
     return len;
 }
+
+void remapTransparentPixels(unsigned char * target, const unsigned char * map, size_t width, size_t height, int transColor, int threshold){
+    // printf("transcolor: %d, threshold: %d\n", transColor, threshold);
+    size_t i = 0, len = width * height;
+    for (; i < len; i++){
+        if (map[i] < threshold) *(target + i) = transColor;
+        // printf("%d,", target[i]);
+    }
+    // printf("\n");
+}