opengl 实现 Photoshop 亮度 对比度 调节功能

源码

VirtualStudio2019的工程。可直接运行

Photoshop的亮度对比度工具

这是photoshop的工具,下面用opengl实现该功能

原理

公式：

y = x - $\frac{255.0-brightness}{2}$* tan(45+44* $\frac{contrast}{255}$ ) + $\frac{255+brightness}{2}$

实现：

    float B = brightness / 255.0;
	float c = contrast / 255.0;
	float k = tan((45 + 44 * c) / 180.0 * PI);

	colorrbg = ((colorrbg*255.0 - 127.5 * (1.0 - B)) * k + 127.5 * (1.0 + B)) / 255.0;

shader

#version 330 core
precision mediump float;

in vec2 TexCoord;
out vec4 outColor;
uniform sampler2D inputTexture;
uniform int brightness;
uniform int contrast;

vec4 tmp(vec3 colorrbg){
    float PI = 3.1415926;
	float B = brightness / 255.0;
	float c = contrast / 255.0;
	float k = tan((45 + 44 * c) / 180.0 * PI);

	colorrbg = ((colorrbg*255.0 - 127.5 * (1.0 - B)) * k + 127.5 * (1.0 + B)) / 255.0;
    return vec4(colorrbg,1.0);
}

void main(){
    
    vec3 tmpColor = texture(inputTexture, TexCoord).rgb;
    outColor = tmp(tmpColor);
}

效果

原图：

亮度+50

亮度-50

对比度-50

对比度+50