gdiplus: Force conversion of 8 bpp grayscale PNG images to 32 bpp BGRA.

dlls/gdiplus/image.c

@@ -3961,7 +3961,37 @@ static GpStatus decode_image_jpeg(IStream* stream, GpImage **image)
 
 static GpStatus decode_image_png(IStream* stream, GpImage **image)
 {
-    return decode_image_wic(stream, &GUID_ContainerFormatPng, png_metadata_reader, image);
+    IWICBitmapDecoder *decoder;
+    IWICBitmapFrameDecode *frame;
+    GpStatus status;
+    HRESULT hr;
+    GUID format;
+    BOOL force_conversion = FALSE;
+
+    status = initialize_decoder_wic(stream, &GUID_ContainerFormatPng, &decoder);
+    if (status != Ok)
+        return status;
+
+    hr = IWICBitmapDecoder_GetFrame(decoder, 0, &frame);
+    if (hr == S_OK)
+    {
+        hr = IWICBitmapFrameDecode_GetPixelFormat(frame, &format);
+        if (hr == S_OK)
+        {
+            if (IsEqualGUID(&format, &GUID_WICPixelFormat8bppGray))
+                force_conversion = TRUE;
+            status = decode_frame_wic(decoder, force_conversion, 0, png_metadata_reader, image);
+        }
+        else
+            status = hresult_to_status(hr);
+
+        IWICBitmapFrameDecode_Release(frame);
+    }
+    else
+        status = hresult_to_status(hr);
+
+    IWICBitmapDecoder_Release(decoder);
+    return status;
 }
 
 static GpStatus decode_image_gif(IStream* stream, GpImage **image)

dlls/gdiplus/tests/image.c

@@ -5014,7 +5014,6 @@ static void test_png_color_formats(void)
 
         status = GdipGetImagePixelFormat(image, &format);
         expect(Ok, status);
-todo_wine_if(td[i].bit_depth == 8 && td[i].color_type == 0)
         ok(format == td[i].format ||
            broken(td[i].bit_depth == 1 && td[i].color_type == 0 && format == PixelFormat32bppARGB), /* XP */
            "%d: expected %#x, got %#x\n", i, td[i].format, format);