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零基础 OpenGL (ES) 学习路线推荐 : OpenGL (ES) 学习目录 >> OpenGL ES 基础
零基础 OpenGL (ES) 学习路线推荐 : OpenGL (ES) 学习目录 >> OpenGL ES 转场
零基础 OpenGL (ES) 学习路线推荐 : OpenGL (ES) 学习目录 >> OpenGL ES 特效
零基础 OpenGL (ES) 学习路线推荐 : OpenGL (ES) 学习目录 >> OpenGL ES 函数
零基础 OpenGL (ES) 学习路线推荐 : OpenGL (ES) 学习目录 >> OpenGL ES GPUImage 使用
零基础 OpenGL (ES) 学习路线推荐 : OpenGL (ES) 学习目录 >> OpenGL ES GLSL 编程
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
使用 GPUImageThresholdEdgeDetectionFilter **,**原图如下：
使用 GPUImageThresholdEdgeDetectionFilter 效果如下：
OpenGL ES Demo 下载地址 : IOS OpenGL ES GPUImage 图像阈值边缘检测 GPUImageThresholdEdgeDetectionFilter
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