implemented image decoding

dlangui.visualdproj

@@ -257,6 +257,7 @@
     <Folder name="graphics">
      <File path="src\dlangui\graphics\drawbuf.d" />
      <File path="src\dlangui\graphics\fonts.d" />
+     <File path="src\dlangui\graphics\images.d" />
     </Folder>
     <Folder name="platforms">
      <Folder name="common">

src/dlangui/graphics/images.d

@@ -0,0 +1,119 @@
+module dlangui.graphics.images;
+
+import dlangui.graphics.drawbuf;
+import std.stream;
+import libpng.png;
+import core.sys.posix.setjmp;
+
+/// load and decode image from stream to ColorDrawBuf, returns null if loading or decoding is failed
+ColorDrawBuf loadImage(InputStream stream) {
+    if (stream is null || !stream.isOpen)
+        return null;
+    // TODO: support more image types
+    return loadPngImage(stream);
+}
+
+class ImageDecodingException : Exception {
+    this(string msg) {
+        super(msg);
+    }
+}
+
+extern (C) void lvpng_error_func (png_structp png, png_const_charp)
+{
+    throw new ImageDecodingException("Error while decoding PNG image");
+}
+
+extern (C) void lvpng_warning_func (png_structp png, png_const_charp)
+{
+    throw new ImageDecodingException("Error while decoding PNG image");
+}
+
+extern (C) void lvpng_read_func(png_structp png, png_bytep buf, png_size_t len)
+{
+    InputStream stream = cast(InputStream)png_get_io_ptr(png);
+    ubyte[] localbuf = new ubyte[len];
+    if (stream.read(localbuf) != len)
+        throw new ImageDecodingException("Error while reading PNG image");
+}
+
+ColorDrawBuf loadPngImage(InputStream stream)
+{
+    png_structp png_ptr = null;
+    png_infop info_ptr = null;
+    png_ptr = png_create_read_struct(PNG_LIBPNG_VER_STRING,
+                                     cast(png_voidp)stream, &lvpng_error_func, &lvpng_warning_func);
+    if ( !png_ptr )
+        return null;
+
+    try {
+        //
+        info_ptr = png_create_info_struct(png_ptr);
+        if (!info_ptr)
+            lvpng_error_func(png_ptr, "cannot create png info struct");
+        png_set_read_fn(png_ptr,
+                        cast(void*)stream, &lvpng_read_func);
+        png_read_info( png_ptr, info_ptr );
+
+
+        png_uint_32 width, height;
+        int bit_depth, color_type, interlace_type;
+        png_get_IHDR(png_ptr, info_ptr, &width, &height,
+                     &bit_depth, &color_type, &interlace_type,
+                     null, null);
+        ColorDrawBuf drawbuf = new ColorDrawBuf(width, height);
+
+        if (color_type & PNG_COLOR_MASK_PALETTE)
+            png_set_palette_to_rgb(png_ptr);
+
+        if (color_type == PNG_COLOR_TYPE_GRAY && bit_depth < 8)
+            png_set_expand_gray_1_2_4_to_8(png_ptr);
+
+        if (png_get_valid(png_ptr, info_ptr, PNG_INFO_tRNS))
+            png_set_tRNS_to_alpha(png_ptr);
+
+        if (bit_depth == 16)
+            png_set_strip_16(png_ptr);
+
+        png_set_invert_alpha(png_ptr);
+
+        if (bit_depth < 8)
+            png_set_packing(png_ptr);
+
+        png_set_filler(png_ptr, 0, PNG_FILLER_AFTER);
+
+        if (color_type == PNG_COLOR_TYPE_GRAY ||
+            color_type == PNG_COLOR_TYPE_GRAY_ALPHA)
+            png_set_gray_to_rgb(png_ptr);
+
+        int number_passes = png_set_interlace_handling(png_ptr);
+        png_set_bgr(png_ptr);
+
+        for (int pass = 0; pass < number_passes; pass++)
+        {
+            for (int y = 0; y < height; y++)
+            {
+                uint * row = drawbuf.scanLine(y);
+                png_read_rows(png_ptr, cast(ubyte **)&row, null, 1);
+            }
+        }
+
+        png_read_end(png_ptr, info_ptr);
+
+        png_destroy_read_struct(&png_ptr, &info_ptr, null);
+
+        return drawbuf;
+    } catch (ImageDecodingException e) {
+        if (png_ptr)
+        {
+            png_destroy_read_struct(&png_ptr, &info_ptr, null);
+        }
+        return null;
+    }
+}
+
+//bool LVPngImageSource::CheckPattern( const lUInt8 * buf, int )
+//{
+    //return( !png_sig_cmp((unsigned char *)buf, (png_size_t)0, 4) );
+//}
+