From bdec75af4d6e16fdeb89a692c3db2f64184dd35c Mon Sep 17 00:00:00 2001
From: mkwong98 <mkwong98@gmail.com>
Date: Fri, 30 Aug 2019 23:38:14 +0800
Subject: [PATCH] Fix premultiplied alpha

---
 Core/HdNesPack.cpp    | 56 ++++++++++++++++++++++---------------------
 Core/HdPackLoader.cpp |  4 ++--
 2 files changed, 31 insertions(+), 29 deletions(-)

diff --git a/Core/HdNesPack.cpp b/Core/HdNesPack.cpp
index 07231bf5..000a4cf0 100644
--- a/Core/HdNesPack.cpp
+++ b/Core/HdNesPack.cpp
@@ -22,9 +22,9 @@ HdNesPack::~HdNesPack()
 void HdNesPack::BlendColors(uint8_t output[4], uint8_t input[4])
 {
 	uint8_t invertedAlpha = 256 - input[3];
-	output[0] = (uint8_t)((input[0] + invertedAlpha * output[0]) >> 8);
-	output[1] = (uint8_t)((input[1] + invertedAlpha * output[1]) >> 8);
-	output[2] = (uint8_t)((input[2] + invertedAlpha * output[2]) >> 8);
+	output[0] = input[0] + (uint8_t)((invertedAlpha * output[0]) >> 8);
+	output[1] = input[1] + (uint8_t)((invertedAlpha * output[1]) >> 8);
+	output[2] = input[2] + (uint8_t)((invertedAlpha * output[2]) >> 8);
 	output[3] = 0xFF;
 }
 
@@ -55,30 +55,32 @@ void HdNesPack::DrawCustomBackground(uint32_t *outputBuffer, uint32_t x, uint32_
 	uint8_t brightness = _hdData->Backgrounds[_backgroundIndex].Brightness;
 	uint32_t width = _hdData->Backgrounds[_backgroundIndex].Data->Width;
 	uint32_t *pngData = _hdData->Backgrounds[_backgroundIndex].data() + (y * _hdData->Scale * width) + (x * _hdData->Scale);
-
-	if(scale == 1) {
-		if(brightness == 255) {
-			*outputBuffer = *pngData;
-		} else {
-			*outputBuffer = AdjustBrightness((uint8_t*)pngData, brightness);
-		}
-	} else {
-		uint32_t *buffer = outputBuffer;
-		for(uint32_t i = 0; i < scale; i++) {
-			memcpy(outputBuffer, pngData, sizeof(uint32_t) * scale);
-			outputBuffer += screenWidth;
-			pngData += width;
-		}
-
-		if(brightness < 255) {
-			for(uint32_t i = 0; i < scale; i++) {
-				for(uint32_t j = 0; j < scale; j++) {
-					*buffer = AdjustBrightness((uint8_t*)buffer, brightness);
-					buffer++;
-				}
-				buffer += screenWidth - scale;
-			}
-		}
+
+	if (scale == 1) {
+		if (brightness == 255) {
+			*outputBuffer = *pngData;
+		}
+		else {
+			*outputBuffer = AdjustBrightness((uint8_t*)pngData, brightness);
+		}
+	}
+	else {
+		uint32_t* buffer = outputBuffer;
+		for (uint32_t i = 0; i < scale; i++) {
+			memcpy(outputBuffer, pngData, sizeof(uint32_t) * scale);
+			outputBuffer += screenWidth;
+			pngData += width;
+		}
+
+		if (brightness < 255) {
+			for (uint32_t i = 0; i < scale; i++) {
+				for (uint32_t j = 0; j < scale; j++) {
+					*buffer = AdjustBrightness((uint8_t*)buffer, brightness);
+					buffer++;
+				}
+				buffer += screenWidth - scale;
+			}
+		}
 	}
 }
 
diff --git a/Core/HdPackLoader.cpp b/Core/HdPackLoader.cpp
index 60ab2e3d..1c1aafd3 100644
--- a/Core/HdPackLoader.cpp
+++ b/Core/HdPackLoader.cpp
@@ -216,7 +216,7 @@ bool HdPackLoader::ProcessImgTag(string src)
 		//premultiply alpha
 		for (int i = 0; i < bitmapInfo.PixelData.size(); ++i) {
 			if (bitmapInfo.PixelData[i] < 0xFF000000) {
-				uint8_t output[4] = (uint8_t*)&(bitmapInfo.PixelData[i]);
+				uint8_t* output = (uint8_t*)(bitmapInfo.PixelData.data() + i);
 				uint8_t alpha = output[3] + 1;
 				output[0] = (uint8_t)((alpha * output[0]) >> 8);
 				output[1] = (uint8_t)((alpha * output[1]) >> 8);
@@ -554,7 +554,7 @@ void HdPackLoader::ProcessBackgroundTag(vector<string> &tokens, vector<HdPackCon
 				//premultiply alpha
 				for (int i = 0; i < bgFileData->PixelData.size(); ++i) {
 					if (bgFileData->PixelData[i] < 0xFF000000) {
-						uint8_t output[4] = (uint8_t*)&(bgFileData->PixelData[i]);
+						uint8_t* output = (uint8_t*)(bgFileData->PixelData.data() + i);
 						uint8_t alpha = output[3] + 1;
 						output[0] = (uint8_t)((alpha * output[0]) >> 8);
 						output[1] = (uint8_t)((alpha * output[1]) >> 8);