IOS OpenGL ES GPUImage 圖像閥值素描，形成有噪點的素描 GPUImageThresholdSketchFilter

目錄一.簡介二.效果演示三.源碼下載四.猜你喜歡零基礎 OpenGL (ES) 學習路線推薦 : OpenGL (ES) 學習目錄 >> OpenGL ES 基礎零基礎 OpenGL (ES) 學習路線推薦 : OpenGL (ES) 學習目錄 >> OpenGL ES 轉場零基礎 O ...

一.簡介
二.效果演示
三.源碼下載
四.猜你喜歡

零基礎 OpenGL (ES) 學習路線推薦 : OpenGL (ES) 學習目錄 >> OpenGL ES 基礎

零基礎 OpenGL (ES) 學習路線推薦 : OpenGL (ES) 學習目錄 >> OpenGL ES 轉場

零基礎 OpenGL (ES) 學習路線推薦 : OpenGL (ES) 學習目錄 >> OpenGL ES 特效

零基礎 OpenGL (ES) 學習路線推薦 : OpenGL (ES) 學習目錄 >> OpenGL ES 函數

零基礎 OpenGL (ES) 學習路線推薦 : OpenGL (ES) 學習目錄 >> OpenGL ES GPUImage 使用

零基礎 OpenGL (ES) 學習路線推薦 : OpenGL (ES) 學習目錄 >> OpenGL ES GLSL 編程

一.簡介

GPUImage 共 125 個濾鏡, 分為四類

1、Color adjustments : 31 filters , 顏色處理相關
2、Image processing : 40 filters , 圖像處理相關.
3、Blending modes : 29 filters , 混合模式相關.
4、Visual effects : 25 filters , 視覺效果相關.

GPUImageThresholdSketchFilter 屬於 GPUImage 圖像視覺效果相關，用於圖像閥值素描，形成有噪點的素描。shader 源碼如下：

/******************************************************************************************/
//@Author:猿說編程
//@Blog(個人博客地址): www.codersrc.com
//@File:IOS – OpenGL ES GPUImage GPUImageThresholdSketchFilter
//@Time:2022/07/02 06:30
//@Motto:不積跬步無以至千里，不積小流無以成江海，程式人生的精彩需要堅持不懈地積累！
/******************************************************************************************/


#if TARGET_IPHONE_SIMULATOR || TARGET_OS_IPHONE
NSString *const kGPUImageThresholdSketchFragmentShaderString = 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;

 const highp vec3 W = vec3(0.2125, 0.7154, 0.0721);

 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;
     float v = -bottomLeftIntensity - 2.0 * leftIntensity - topLeftIntensity + bottomRightIntensity + 2.0 * rightIntensity + topRightIntensity;

     float mag = (length(vec2(h, v)) * edgeStrength);
     mag = step(threshold, mag);
     mag = 1.0 - mag;

     gl_FragColor = vec4(vec3(mag), 1.0);
 }
);
#else
NSString *const kGPUImageThresholdSketchFragmentShaderString = 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;

 const vec3 W = vec3(0.2125, 0.7154, 0.0721);

 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;
     float v = -bottomLeftIntensity - 2.0 * leftIntensity - topLeftIntensity + bottomRightIntensity + 2.0 * rightIntensity + topRightIntensity;

     float mag = 1.0 - length(vec2(h, v) * edgeStrength);
     mag = step(threshold, mag);

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