From dd75517d61f93d6fcf31c7d83f5b2d89d3228756 Mon Sep 17 00:00:00 2001
From: lb_ii <lolbot_iichan@mail.ru>
Date: Sun, 27 Jun 2021 21:16:43 +0300
Subject: [PATCH] IMAGE: Use 0-bit alpha for non-transparent PNGs

---
 image/png.cpp | 12 +++++++-----
 image/png.h   |  2 +-
 2 files changed, 8 insertions(+), 6 deletions(-)

diff --git a/image/png.cpp b/image/png.cpp
index fc4134b2e6c..b8ef5d3f96a 100644
--- a/image/png.cpp
+++ b/image/png.cpp
@@ -63,11 +63,11 @@ void PNGDecoder::destroy() {
 	_palette = NULL;
 }
 
-Graphics::PixelFormat PNGDecoder::getByteOrderRgbaPixelFormat() const {
+Graphics::PixelFormat PNGDecoder::getByteOrderRgbaPixelFormat(bool isAlpha) const {
 #ifdef SCUMM_BIG_ENDIAN
-	return Graphics::PixelFormat(4, 8, 8, 8, 8, 24, 16, 8, 0);
+	return Graphics::PixelFormat(4, 8, 8, 8, isAlpha ? 8 : 0, 24, 16, 8, 0);
 #else
-	return Graphics::PixelFormat(4, 8, 8, 8, 8, 0, 8, 16, 24);
+	return Graphics::PixelFormat(4, 8, 8, 8, isAlpha ? 8 : 0, 0, 8, 16, 24);
 #endif
 }
 
@@ -201,7 +201,7 @@ bool PNGDecoder::loadStream(Common::SeekableReadStream &stream) {
 		}
 
 		_outputSurface->create(width, height,
-			hasRgbaPalette ? getByteOrderRgbaPixelFormat() : Graphics::PixelFormat::createFormatCLUT8());
+			hasRgbaPalette ? getByteOrderRgbaPixelFormat(true) : Graphics::PixelFormat::createFormatCLUT8());
 		png_set_packing(pngPtr);
 
 		if (hasRgbaPalette) {
@@ -219,11 +219,13 @@ bool PNGDecoder::loadStream(Common::SeekableReadStream &stream) {
 			_palette = nullptr;
 		}
 	} else {
+ 		bool isAlpha = (colorType & PNG_COLOR_MASK_ALPHA);
 		if (png_get_valid(pngPtr, infoPtr, PNG_INFO_tRNS)) {
+ 			isAlpha = true;
 			png_set_expand(pngPtr);
 		}
 
-		_outputSurface->create(width, height, getByteOrderRgbaPixelFormat());
+		_outputSurface->create(width, height, getByteOrderRgbaPixelFormat(isAlpha));
 		if (!_outputSurface->getPixels()) {
 			error("Could not allocate memory for output image.");
 		}
diff --git a/image/png.h b/image/png.h
index 59f0aa2dc67..f6057587251 100644
--- a/image/png.h
+++ b/image/png.h
@@ -67,7 +67,7 @@ public:
 	void setSkipSignature(bool skip) { _skipSignature = skip; }
 	void setKeepTransparencyPaletted(bool keep) { _keepTransparencyPaletted = keep; }
 private:
-	Graphics::PixelFormat getByteOrderRgbaPixelFormat() const;
+	Graphics::PixelFormat getByteOrderRgbaPixelFormat(bool isAlpha) const;
 
 	byte *_palette;
 	uint16 _paletteColorCount;