slang-shaders/crt/shaders/guest/avg-lum.slang

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#version 450
/*
Average Luminance Shader
Copyright (C) 2018 guest(r) - guest.r@gmail.com
This program is free software; you can redistribute it and/or
modify it under the terms of the GNU General Public License
as published by the Free Software Foundation; either version 2
of the License, or (at your option) any later version.
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program; if not, write to the Free Software
Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
Thanks to HunterK for the mipmap hint. :D
*/
layout(push_constant) uniform Push
{
vec4 SourceSize;
vec4 OriginalSize;
vec4 OutputSize;
uint FrameCount;
float grade;
} params;
#pragma parameter grade "Blooming grade" 0.70 0.10 1.0 0.05
layout(std140, set = 0, binding = 0) uniform UBO
{
mat4 MVP;
} global;
#pragma stage vertex
layout(location = 0) in vec4 Position;
layout(location = 1) in vec2 TexCoord;
layout(location = 0) out vec2 vTexCoord;
void main()
{
gl_Position = global.MVP * Position;
vTexCoord = TexCoord;
}
#pragma stage fragment
layout(location = 0) in vec2 vTexCoord;
layout(location = 0) out vec4 FragColor;
layout(set = 0, binding = 2) uniform sampler2D Source;
void main()
{
float mip_level = max(log2(params.SourceSize.x), log2(params.SourceSize.y));
float black_compensation = (params.SourceSize.x*params.SourceSize.y)/(params.SourceSize.x*params.SourceSize.y);
float lum = length(textureLod(Source, vTexCoord.xy, mip_level).rgb * black_compensation);
lum = lum * inversesqrt(3.0);
FragColor = vec4(pow(lum, params.grade));
}