From 0a07f4c144f29f7a7de48c0d7b1ec2cc0a50d1a2 Mon Sep 17 00:00:00 2001
From: Christoph Oelckers <coelckers@users.noreply.github.com>
Date: Thu, 22 Mar 2018 23:57:14 +0100
Subject: [PATCH] - fixed alpha texture generation for OpenGL rendering.

The old logic used a translation table that does not work with color images, it was designed to handle 8 bit grayscale images.
So now, it creates a true color buffer and then turns it into a texture with R,G,B = 255 and the alpha channel set to the grayscale value.

This was also the reason why crosshairs made from 32 bit PNGs did not show correctly.
---
 src/gl/renderer/gl_renderstate.h |  2 +-
 src/gl/textures/gl_material.cpp  | 51 ++++++++++++++++----------------
 src/textures/pcxtexture.cpp      |  1 -
 3 files changed, 27 insertions(+), 27 deletions(-)

diff --git a/src/gl/renderer/gl_renderstate.h b/src/gl/renderer/gl_renderstate.h
index 4e844c9795..34a030f8a0 100644
--- a/src/gl/renderer/gl_renderstate.h
+++ b/src/gl/renderer/gl_renderstate.h
@@ -145,7 +145,7 @@ public:
 	void SetMaterial(FMaterial *mat, int clampmode, int translation, int overrideshader, bool alphatexture)
 	{
 		// alpha textures need special treatment in the legacy renderer because withouz shaders they need a different texture.
-		if (alphatexture &&  gl.legacyMode) translation = TRANSLATION(TRANSLATION_Standard, 8);
+		if (alphatexture &&  gl.legacyMode) translation = INT_MAX;
 		
 		if (mat->tex->bHasCanvas)
 		{
diff --git a/src/gl/textures/gl_material.cpp b/src/gl/textures/gl_material.cpp
index 98f0559d94..6ac7eb05ac 100644
--- a/src/gl/textures/gl_material.cpp
+++ b/src/gl/textures/gl_material.cpp
@@ -213,31 +213,27 @@ unsigned char * FGLTexture::CreateTexBuffer(int translation, int & w, int & h, F
 
 	FBitmap bmp(buffer, W*4, W, H);
 
-	if (translation <= 0)
+	if (translation <= 0 || alphatrans)
 	{
-		// Q: Is this special treatment still needed? Needs to be checked.
-		if (tex->bComplex)
+		int trans = tex->CopyTrueColorPixels(&bmp, exx, exx);
+		tex->CheckTrans(buffer, W*H, trans);
+		isTransparent = tex->gl_info.mIsTransparent;
+		if (bIsTransparent == -1) bIsTransparent = isTransparent;
+		// alpha texture for legacy mode
+		if (alphatrans)
 		{
-			FBitmap imgCreate;
-
-			// The texture contains special processing so it must be fully composited before being converted as a whole.
-			if (imgCreate.Create(W, H))
+			for (int i = 0; i < W*H; i++)
 			{
-				memset(imgCreate.GetPixels(), 0, W * H * 4);
-				int trans = tex->CopyTrueColorPixels(&imgCreate, exx, exx);
-				bmp.CopyPixelDataRGB(0, 0, imgCreate.GetPixels(), W, H, 4, W * 4, 0, CF_BGRA);
-				tex->CheckTrans(buffer, W*H, trans);
-				isTransparent = tex->gl_info.mIsTransparent;
-				if (bIsTransparent == -1) bIsTransparent = isTransparent;
+				int b = buffer[4 * i];
+				int g = buffer[4 * i + 1];
+				int r = buffer[4 * i + 2];
+				int gray = Luminance(r, g, b);
+				buffer[4 * i] = 255;
+				buffer[4 * i + 1] = 255;
+				buffer[4 * i + 2] = 255;
+				buffer[4 * i + 3] = (buffer[4 * i + 3] * gray) >> 8;
 			}
 		}
-		else
-		{
-			int trans = tex->CopyTrueColorPixels(&bmp, exx, exx);
-			tex->CheckTrans(buffer, W*H, trans);
-			isTransparent = tex->gl_info.mIsTransparent;
-			if (bIsTransparent == -1) bIsTransparent = isTransparent;
-		}
 	}
 	else
 	{
@@ -282,13 +278,18 @@ FHardwareTexture *FGLTexture::CreateHwTexture()
 const FHardwareTexture *FGLTexture::Bind(int texunit, int clampmode, int translation, FTexture *hirescheck)
 {
 	int usebright = false;
-	bool alphatrans = false;
+	bool alphatrans = translation == INT_MAX;	// This is only needed for legacy mode because no texture combine setting allows using the color as alpha.
 
-	if (translation <= 0) translation = -translation;
-	else
+	if (!alphatrans)
 	{
-		alphatrans = (gl.legacyMode && uint32_t(translation) == TRANSLATION(TRANSLATION_Standard, 8));
-		translation = GLTranslationPalette::GetInternalTranslation(translation);
+		if (translation <= 0)
+		{
+			translation = -translation;
+		}
+		else
+		{
+			translation = GLTranslationPalette::GetInternalTranslation(translation);
+		}
 	}
 
 	bool needmipmap = (clampmode <= CLAMP_XY);
diff --git a/src/textures/pcxtexture.cpp b/src/textures/pcxtexture.cpp
index 4d7e9d94f2..1a9f73841b 100644
--- a/src/textures/pcxtexture.cpp
+++ b/src/textures/pcxtexture.cpp
@@ -126,7 +126,6 @@ FTexture * PCXTexture_TryCreate(FileReader & file, int lumpnum)
 	if (hdr.version != 0 && hdr.version != 2 && hdr.version != 3 && hdr.version != 4 && hdr.version != 5) return NULL;
 	if (hdr.bitsPerPixel != 1 && hdr.bitsPerPixel != 8 && hdr.bitsPerPixel != 4) return NULL; 
 	if (hdr.bitsPerPixel == 1 && hdr.numColorPlanes !=1 && hdr.numColorPlanes != 4) return NULL;
-	if (hdr.bitsPerPixel == 4 && hdr.numColorPlanes != 1) return NULL;
 	if (hdr.bitsPerPixel == 8 && hdr.bytesPerScanLine != ((hdr.xmax - hdr.xmin + 2)&~1)) return NULL;
 
 	for (int i = 0; i < 54; i++)