[PATCH 1/2] windowscodecs: Byte swap png read/write for 16-bpp data.

[Vincent Povirk]

From: Bryon Roche <kain at kain.org>

Wine-Bug: https://bugs.winehq.org/show_bug.cgi?id=46558
Signed-off-by: Vincent Povirk <vincent at codeweavers.com>
---
 dlls/windowscodecs/pngformat.c | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/dlls/windowscodecs/pngformat.c b/dlls/windowscodecs/pngformat.c
index db0fa9ed507..a79e7e1cffa 100644
--- a/dlls/windowscodecs/pngformat.c
+++ b/dlls/windowscodecs/pngformat.c
@@ -332,6 +332,7 @@ MAKE_FUNCPTR(png_set_strip_16);
 MAKE_FUNCPTR(png_set_tRNS);
 MAKE_FUNCPTR(png_set_tRNS_to_alpha);
 MAKE_FUNCPTR(png_set_write_fn);
+MAKE_FUNCPTR(png_set_swap);
 MAKE_FUNCPTR(png_read_end);
 MAKE_FUNCPTR(png_read_image);
 MAKE_FUNCPTR(png_read_info);
@@ -398,6 +399,7 @@ static void *load_libpng(void)
         LOAD_FUNCPTR(png_set_tRNS);
         LOAD_FUNCPTR(png_set_tRNS_to_alpha);
         LOAD_FUNCPTR(png_set_write_fn);
+        LOAD_FUNCPTR(png_set_swap);
         LOAD_FUNCPTR(png_read_end);
         LOAD_FUNCPTR(png_read_image);
         LOAD_FUNCPTR(png_read_info);
@@ -642,6 +644,10 @@ static HRESULT WINAPI PngDecoder_Initialize(IWICBitmapDecoder *iface, IStream *p
     color_type = ppng_get_color_type(This->png_ptr, This->info_ptr);
     bit_depth = ppng_get_bit_depth(This->png_ptr, This->info_ptr);
 
+    /* PNGs with bit-depth greater than 8 are network byte order. Windows does not expect this. */
+    if (bit_depth > 8) 
+        ppng_set_swap(This->png_ptr);
+
     /* check for color-keyed alpha */
     transparency = ppng_get_tRNS(This->png_ptr, This->info_ptr, &trans, &num_trans, &trans_values);
 
@@ -1643,6 +1649,10 @@ static HRESULT WINAPI PngFrameEncode_WritePixels(IWICBitmapFrameEncode *iface,
             }
         }
 
+        /* Tell PNG we need to byte swap if writing a >8-bpp image */
+        if (This->format->bit_depth > 8)
+            ppng_set_swap(This->png_ptr);
+
         ppng_set_IHDR(This->png_ptr, This->info_ptr, This->width, This->height,
             This->format->bit_depth, This->format->color_type,
             This->interlace ? PNG_INTERLACE_ADAM7 : PNG_INTERLACE_NONE,
-- 
2.17.1