converted skiaserve PNGs from RGBA to RGB

tools/skiaserve/skiaserve.cpp

 /*
  * Copyright 2016 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #include "GrCaps.h"
 #include "GrContextFactory.h"
 #include "SkCanvas.h"
@@ skipping 88 matching lines @@
 }
 
 static void write_png(const png_bytep rgba, png_uint_32 width, png_uint_32 height, SkWStream& out) {
     png_structp png = png_create_write_struct(PNG_LIBPNG_VER_STRING, NULL, NULL, NULL);
     SkASSERT(png != nullptr);
     png_infop info_ptr = png_create_info_struct(png);
     SkASSERT(info_ptr != nullptr);
     if (setjmp(png_jmpbuf(png))) {
         SkFAIL("png encode error");
     }
-    png_set_IHDR(png, info_ptr, width, height, 8, PNG_COLOR_TYPE_RGBA, PNG_INTERLACE_NONE,
+    png_set_IHDR(png, info_ptr, width, height, 8, PNG_COLOR_TYPE_RGB, PNG_INTERLACE_NONE,
                  PNG_COMPRESSION_TYPE_DEFAULT, PNG_FILTER_TYPE_DEFAULT);
     png_set_compression_level(png, 1);
     png_bytepp rows = (png_bytepp) sk_malloc_throw(height * sizeof(png_byte*));
+    png_bytep pixels = (png_bytep) sk_malloc_throw(width * height * 3);
     for (png_size_t y = 0; y < height; ++y) {
-        rows[y] = (png_bytep) rgba + y * width * 4;
+        const png_bytep src = rgba + y * width * 4;
+        rows[y] = pixels + y * width * 3;
+        // convert from RGBA to RGB
+        for (png_size_t x = 0; x < width; ++x) {
+            rows[y][x * 3] = src[x * 4];
+            rows[y][x * 3 + 1] = src[x * 4 + 1];
+            rows[y][x * 3 + 2] = src[x * 4 + 2];
+        }
     }
     png_set_filter(png, 0, PNG_NO_FILTERS);
     png_set_rows(png, info_ptr, &rows[0]);
     png_set_write_fn(png, &out, write_png_callback, NULL);
     png_write_png(png, info_ptr, PNG_TRANSFORM_IDENTITY, NULL);
     png_destroy_write_struct(&png, NULL);
     sk_free(rows);
 }
 
 SkData* writeCanvasToPng(SkCanvas* canvas) {
@@ skipping 498 matching lines @@
     MHD_stop_daemon(daemon);
     return 0;
 }
 
 #if !defined SK_BUILD_FOR_IOS
 int main(int argc, char** argv) {
     SkCommandLineFlags::Parse(argc, argv);
     return skiaserve_main();
 }
 #endif