IOS – OpenGL ES 调节图像阴影 GPUImageHighlightShadowFilter

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猿说编程[Python和C]

发布于 2023-03-19 09:48:38

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发布于 2023-03-19 09:48:38

文章被收录于专栏：猿说编程猿说编程

一.简介

GPUImage 共 125 个滤镜, 分为四类

1、Color adjustments : 31 filters , 颜色处理相关 2、Image processing : 40 filters , 图像处理相关. 3、Blending modes : 29 filters , 混合模式相关. 4、Visual effects : 25 filters , 视觉效果相关.

GPUImageHighlightShadowFilter 属于 GPUImage 颜色处理相关，用来处理图片阴影，shader 源码如下：

/******************************************************************************************/
//@Author:猿说编程
//@Blog(个人博客地址): www.codersrc.com
//@File:IOS – OpenGL ES 调节图像阴影 GPUImageHighlightShadowFilter
//@Time:2022/03/17 07:30
//@Motto:不积跬步无以至千里，不积小流无以成江海，程序人生的精彩需要坚持不懈地积累！
/******************************************************************************************/


#if TARGET_IPHONE_SIMULATOR || TARGET_OS_IPHONE
NSString *const kGPUImageHighlightShadowFragmentShaderString = SHADER_STRING
(
uniform sampler2D inputImageTexture;
varying highp vec2 textureCoordinate;

uniform lowp float shadows;
uniform lowp float highlights;

const mediump vec3 luminanceWeighting = vec3(0.3, 0.3, 0.3);

void main()
{
    lowp vec4 source = texture2D(inputImageTexture, textureCoordinate);
    mediump float luminance = dot(source.rgb, luminanceWeighting);

    mediump float shadow = clamp((pow(luminance, 1.0/(shadows+1.0)) + (-0.76)*pow(luminance, 2.0/(shadows+1.0))) - luminance, 0.0, 1.0);
    mediump float highlight = clamp((1.0 - (pow(1.0-luminance, 1.0/(2.0-highlights)) + (-0.8)*pow(1.0-luminance, 2.0/(2.0-highlights)))) - luminance, -1.0, 0.0);
    lowp vec3 result = vec3(0.0, 0.0, 0.0) + ((luminance + shadow + highlight) - 0.0) * ((source.rgb - vec3(0.0, 0.0, 0.0))/(luminance - 0.0));

    gl_FragColor = vec4(result.rgb, source.a);
}
);
#else
NSString *const kGPUImageHighlightShadowFragmentShaderString = SHADER_STRING
(
 uniform sampler2D inputImageTexture;
 varying vec2 textureCoordinate;

 uniform float shadows;
 uniform float highlights;

 const vec3 luminanceWeighting = vec3(0.3, 0.3, 0.3);

 void main()
 {
    vec4 source = texture2D(inputImageTexture, textureCoordinate);
    float luminance = dot(source.rgb, luminanceWeighting);

    float shadow = clamp((pow(luminance, 1.0/(shadows+1.0)) + (-0.76)*pow(luminance, 2.0/(shadows+1.0))) - luminance, 0.0, 1.0);
    float highlight = clamp((1.0 - (pow(1.0-luminance, 1.0/(2.0-highlights)) + (-0.8)*pow(1.0-luminance, 2.0/(2.0-highlights)))) - luminance, -1.0, 0.0);
    vec3 result = vec3(0.0, 0.0, 0.0) + ((luminance + shadow + highlight) - 0.0) * ((source.rgb - vec3(0.0, 0.0, 0.0))/(luminance - 0.0));

    gl_FragColor = vec4(result.rgb, source.a);
 }
);
#endif