IOS OpenGL ES GPUImage 图像阈值边缘检测GPUImageThresholdEdgeDetectionFilter

一.简介
二.效果演示
三.源码下载
四.猜你喜欢

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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.

GPUImageThresholdEdgeDetectionFilter 属于 GPUImage 图像视觉效果相关，用于图像阈值边缘检测。shader 源码如下：

/******************************************************************************************/
//@Author:猿说编程
//@Blog(个人博客地址): www.codersrc.com
//@File:IOS – OpenGL ES GPUImage GPUImageThresholdEdgeDetectionFilter
//@Time:2022/06/26 06:30
//@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！
/******************************************************************************************/

// Invert the colorspace for a sketch
#if TARGET_IPHONE_SIMULATOR || TARGET_OS_IPHONE
NSString *const kGPUImageThresholdEdgeDetectionFragmentShaderString = SHADER_STRING
(
 precision highp float;

 varying vec2 textureCoordinate;
 varying vec2 leftTextureCoordinate;
 varying vec2 rightTextureCoordinate;

 varying vec2 topTextureCoordinate;
 varying vec2 topLeftTextureCoordinate;
 varying vec2 topRightTextureCoordinate;

 varying vec2 bottomTextureCoordinate;
 varying vec2 bottomLeftTextureCoordinate;
 varying vec2 bottomRightTextureCoordinate;

 uniform sampler2D inputImageTexture;
 uniform lowp float threshold;

 uniform float edgeStrength;

 void main()
 {
//     float bottomLeftIntensity = texture2D(inputImageTexture, bottomLeftTextureCoordinate).r;
//     float topRightIntensity = texture2D(inputImageTexture, topRightTextureCoordinate).r;
//     float topLeftIntensity = texture2D(inputImageTexture, topLeftTextureCoordinate).r;
//     float bottomRightIntensity = texture2D(inputImageTexture, bottomRightTextureCoordinate).r;
     float leftIntensity = texture2D(inputImageTexture, leftTextureCoordinate).r;
     float rightIntensity = texture2D(inputImageTexture, rightTextureCoordinate).r;
     float bottomIntensity = texture2D(inputImageTexture, bottomTextureCoordinate).r;
     float topIntensity = texture2D(inputImageTexture, topTextureCoordinate).r;
     float centerIntensity = texture2D(inputImageTexture, textureCoordinate).r;
//     float h = -topLeftIntensity - 2.0 * topIntensity - topRightIntensity + bottomLeftIntensity + 2.0 * bottomIntensity + bottomRightIntensity;
//     float v = -bottomLeftIntensity - 2.0 * leftIntensity - topLeftIntensity + bottomRightIntensity + 2.0 * rightIntensity + topRightIntensity;
//     float h = -topLeftIntensity - 2.0 * topIntensity - topRightIntensity + leftIntensity + 2.0 * centerIntensity + rightIntensity;
//     float v = -bottomLeftIntensity - 2.0 * leftIntensity - topLeftIntensity + bottomIntensity + 2.0 * centerIntensity + topIntensity;
     float h = (centerIntensity - topIntensity) + (bottomIntensity - centerIntensity);
     float v = (centerIntensity - leftIntensity) + (rightIntensity - centerIntensity);
//     float h = (centerIntensity - topIntensity);
//     float j = (topIntensity - centerIntensity);
//     h = max(h,j);
//     j = abs(h);
//     float v = (centerIntensity - leftIntensity);

    float mag = length(vec2(h, v)) * edgeStrength;
     mag = step(threshold, mag);

//     float mag = abs(h);

//     gl_FragColor = vec4(h, h, h, 1.0);
//     gl_FragColor = vec4(texture2D(inputImageTexture, textureCoordinate));
//     gl_FragColor = vec4(h, centerIntensity, j, 1.0);
     gl_FragColor = vec4(mag, mag, mag, 1.0);
 }
);
#else
NSString *const kGPUImageThresholdEdgeDetectionFragmentShaderString = SHADER_STRING
(
 varying vec2 textureCoordinate;
 varying vec2 leftTextureCoordinate;
 varying vec2 rightTextureCoordinate;

 varying vec2 topTextureCoordinate;
 varying vec2 topLeftTextureCoordinate;
 varying vec2 topRightTextureCoordinate;

 varying vec2 bottomTextureCoordinate;
 varying vec2 bottomLeftTextureCoordinate;
 varying vec2 bottomRightTextureCoordinate;

 uniform sampler2D inputImageTexture;
 uniform float threshold;

 uniform float edgeStrength;

 void main()
 {
     float bottomLeftIntensity = texture2D(inputImageTexture, bottomLeftTextureCoordinate).r;
     float topRightIntensity = texture2D(inputImageTexture, topRightTextureCoordinate).r;
     float topLeftIntensity = texture2D(inputImageTexture, topLeftTextureCoordinate).r;
     float bottomRightIntensity = texture2D(inputImageTexture, bottomRightTextureCoordinate).r;
     float leftIntensity = texture2D(inputImageTexture, leftTextureCoordinate).r;
     float rightIntensity = texture2D(inputImageTexture, rightTextureCoordinate).r;
     float bottomIntensity = texture2D(inputImageTexture, bottomTextureCoordinate).r;
     float topIntensity = texture2D(inputImageTexture, topTextureCoordinate).r;
     float h = -topLeftIntensity - 2.0 * topIntensity - topRightIntensity + bottomLeftIntensity + 2.0 * bottomIntensity + bottomRightIntensity;
     h = max(0.0, h);
     float v = -bottomLeftIntensity - 2.0 * leftIntensity - topLeftIntensity + bottomRightIntensity + 2.0 * rightIntensity + topRightIntensity;
     v = max(0.0, v);

     float mag = length(vec2(h, v)) * edgeStrength;
     mag = step(threshold, mag);

     gl_FragColor = vec4(vec3(mag), 1.0);
 }
);
#endif