From 333560086de84cddacccff034afb887d76dc728b Mon Sep 17 00:00:00 2001
From: "alexey.lysiuk" <alexey.lysiuk@gmail.com>
Date: Mon, 2 May 2016 10:35:38 +0300
Subject: [PATCH] Calculate color values for gamma correction directly in
 shader

Gamma table texture is no longer needed
---
 src/posix/cocoa/i_video.mm                    | 32 +++----------------
 src/posix/cocoa/sdlglvideo.h                  |  6 ----
 wadsrc/static/shaders/glsl/gammacorrection.fp | 30 +++++++++--------
 3 files changed, 21 insertions(+), 47 deletions(-)

diff --git a/src/posix/cocoa/i_video.mm b/src/posix/cocoa/i_video.mm
index fc415535f..069239b48 100644
--- a/src/posix/cocoa/i_video.mm
+++ b/src/posix/cocoa/i_video.mm
@@ -1150,19 +1150,14 @@ void CocoaFrameBuffer::Flip()
 // ---------------------------------------------------------------------------
 
 
-static const uint32_t GAMMA_TABLE_ALPHA = 0xFF000000;
-
-
 SDLGLFB::SDLGLFB(void*, const int width, const int height, int, int, const bool fullscreen)
 : DFrameBuffer(width, height)
 , m_lock(-1)
 , m_isUpdatePending(false)
-, m_gammaTexture(GAMMA_TABLE_SIZE, 1, true)
 {
 }
 
 SDLGLFB::SDLGLFB()
-: m_gammaTexture(0, 0, false)
 {
 }
 
@@ -1243,26 +1238,6 @@ void SDLGLFB::SwapBuffers()
 
 void SDLGLFB::SetGammaTable(WORD* table)
 {
-	const WORD* const red   = &table[  0];
-	const WORD* const green = &table[256];
-	const WORD* const blue  = &table[512];
-
-	for (size_t i = 0; i < GAMMA_TABLE_SIZE; ++i)
-	{
-		// Convert 16 bits colors to 8 bits by dividing on 256
-
-		const uint32_t r =   red[i] >> 8;
-		const uint32_t g = green[i] >> 8;
-		const uint32_t b =  blue[i] >> 8;
-
-		m_gammaTable[i] = GAMMA_TABLE_ALPHA + (b << 16) + (g << 8) + r;
-	}
-
-	m_gammaTexture.CreateTexture(
-		reinterpret_cast<unsigned char*>(m_gammaTable),
-		GAMMA_TABLE_SIZE, 1, 1, false, 0);
-
-	GLRenderer->mSamplerManager->Bind(1, CLAMP_NOFILTER, -1);
 }
 
 
@@ -1278,12 +1253,15 @@ void BoundTextureSetFilter(const GLenum target, const GLint filter)
 	glTexParameteri(target, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_EDGE);
 }
 
+EXTERN_CVAR(Float, vid_brightness)
+EXTERN_CVAR(Float, vid_contrast)
+
 void BoundTextureDraw2D(const GLsizei width, const GLsizei height)
 {
 	gl_RenderState.SetEffect(EFF_GAMMACORRECTION);
 	gl_RenderState.SetTextureMode(TM_OPAQUE);
 	gl_RenderState.AlphaFunc(GL_GEQUAL, 0.f);
-	gl_RenderState.ResetColor();
+	gl_RenderState.SetColor(Gamma, vid_contrast, vid_brightness);
 	gl_RenderState.Apply();
 
 	static const float x  = 0.f;
@@ -1490,9 +1468,7 @@ void CocoaOpenGLFrameBuffer::GetScreenshotBuffer(const BYTE*& buffer, int& pitch
 void CocoaOpenGLFrameBuffer::DrawRenderTarget()
 {
 	m_renderTarget.Unbind();
-
 	m_renderTarget.GetColorTexture().Bind(0, 0, false);
-	m_gammaTexture.Bind(1, 0, false);
 
 	if (rbOpts.dirty)
 	{
diff --git a/src/posix/cocoa/sdlglvideo.h b/src/posix/cocoa/sdlglvideo.h
index aac8992d9..439b4d5ce 100644
--- a/src/posix/cocoa/sdlglvideo.h
+++ b/src/posix/cocoa/sdlglvideo.h
@@ -70,12 +70,6 @@ protected:
 
 	static const bool   m_supportsGamma = true;
 
-	FHardwareTexture    m_gammaTexture;
-
-	static const size_t GAMMA_TABLE_SIZE = 256;
-	uint32_t            m_gammaTable[GAMMA_TABLE_SIZE];
-
-
 	SDLGLFB();
 
 	void InitializeState();
diff --git a/wadsrc/static/shaders/glsl/gammacorrection.fp b/wadsrc/static/shaders/glsl/gammacorrection.fp
index f8c2cf6a3..1deb1a600 100644
--- a/wadsrc/static/shaders/glsl/gammacorrection.fp
+++ b/wadsrc/static/shaders/glsl/gammacorrection.fp
@@ -1,24 +1,28 @@
 uniform sampler2D tex;
-uniform sampler2D texture2;
 
 in vec4 vTexCoord;
-
-void applyGamma(int channel)
-{
-	vec4 color = texture(texture2, vec2(FragColor[channel], 0.0));
-	FragColor[channel] = color[channel];
-}
+in vec4 vColor;
 
 void main()
 {
-	FragColor = texture(tex, vTexCoord.st);
+	vec3 color = texture(tex, vTexCoord.st).rgb;
 
 //	/* DEBUG */ if (vTexCoord.x > 0.5)
 	{
-		applyGamma(0);
-		applyGamma(1);
-		applyGamma(2);
+		// Apply contrast
+		float contrast = clamp(vColor.y, 0.1, 3.0);
+		color = color.rgb * contrast - (contrast - 1.0) * 0.5;
+
+		// Apply gamma
+		float gamma = clamp(vColor.x, 0.1, 4.0);
+		color = sign(color) * pow(abs(color), vec3(1.0 / gamma));
+
+		// Apply brightness
+		float brightness = clamp(vColor.z, -0.8, 0.8);
+		color += brightness * 0.5;
+
+		color = clamp(color, 0.0, 1.0);
 	}
-	
-	FragColor.a = 1.0;
+
+	FragColor = vec4(color, 1.0);
 }