IOS – OpenGL ES 绘制十字 GPUImageCrosshairGenerator-猿说编程

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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

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.

GPUImageCrosshairGenerator 属于 GPUImage 图像处理相关，用来绘制十字，shader 源码如下：



/******************************************************************************************/
//@Author:猿说编程
//@Blog(个人博客地址): www.codersrc.com
//@File:IOS – OpenGL ES 绘制十字 GPUImageCrosshairGenerator
//@Time:2022/04/18 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！
/******************************************************************************************/


NSString *const kGPUImageCrosshairVertexShaderString = SHADER_STRING
(
 attribute vec4 position;
 
 uniform float crosshairWidth;
 
 varying vec2 centerLocation;
 varying float pointSpacing;
 
 void main()
 {
     gl_Position = vec4(((position.xy * 2.0) - 1.0), 0.0, 1.0);
     gl_PointSize = crosshairWidth + 1.0;
     pointSpacing = 1.0 / crosshairWidth;
     centerLocation = vec2(pointSpacing * ceil(crosshairWidth / 2.0), pointSpacing * ceil(crosshairWidth / 2.0));
 }
);

#if TARGET_IPHONE_SIMULATOR || TARGET_OS_IPHONE
NSString *const kGPUImageCrosshairFragmentShaderString = SHADER_STRING
(
 uniform lowp vec3 crosshairColor;

 varying highp vec2 centerLocation;
 varying highp float pointSpacing;

 void main()
 {
     lowp vec2 distanceFromCenter = abs(centerLocation - gl_PointCoord.xy);
     lowp float axisTest = step(pointSpacing, gl_PointCoord.y) * step(distanceFromCenter.x, 0.09) + step(pointSpacing, gl_PointCoord.x) * step(distanceFromCenter.y, 0.09);

     gl_FragColor = vec4(crosshairColor * axisTest, axisTest);
//     gl_FragColor = vec4(distanceFromCenterInX, distanceFromCenterInY, 0.0, 1.0);
 }
);
#else
NSString *const kGPUImageCrosshairFragmentShaderString = SHADER_STRING
(
 GPUImageEscapedHashIdentifier(version 120)\n
 
 uniform vec3 crosshairColor;
 
 varying vec2 centerLocation;
 varying float pointSpacing;
 
 void main()
 {
     vec2 distanceFromCenter = abs(centerLocation - gl_PointCoord.xy);
     float axisTest = step(pointSpacing, gl_PointCoord.y) * step(distanceFromCenter.x, 0.09) + step(pointSpacing, gl_PointCoord.x) * step(distanceFromCenter.y, 0.09);
     
     gl_FragColor = vec4(crosshairColor * axisTest, axisTest);
     //     gl_FragColor = vec4(distanceFromCenterInX, distanceFromCenterInY, 0.0, 1.0);
 }
);
#endif