IOS OpenGL ES GPUImage 图像显示亮度最高的像素,其他为黑 GPUImageThresho ...

张国伟 · 2022-8-25 18:11:30

零基础 OpenGL (ES) 学习路线推荐 : OpenGL (ES) 学习目录 >> OpenGL ES 基础
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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.

GPUImageThresholdedNonMaximumSuppressionFilter属于 GPUImage 图像视觉效果相关，用来处理**图像图像显示亮度最高的像素,其他为黑效果**，相比于 GPUImageNonMaximumSuppressionFilter ，GPUImageThresholdedNonMaximumSuppressionFilter像素丢失更多。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 图像显示亮度最高的像素,其他为黑 GPUImageThresholdedNonMaximumSuppressionFilter
//@Time:2022/06/21 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！
/******************************************************************************************/
#if TARGET_IPHONE_SIMULATOR || TARGET_OS_IPHONE
NSString *const kGPUImageThresholdedNonMaximumSuppressionFragmentShaderString = SHADER_STRING
(
uniform sampler2D inputImageTexture;
varying highp vec2 textureCoordinate;
varying highp vec2 leftTextureCoordinate;
varying highp vec2 rightTextureCoordinate;
varying highp vec2 topTextureCoordinate;
varying highp vec2 topLeftTextureCoordinate;
varying highp vec2 topRightTextureCoordinate;
varying highp vec2 bottomTextureCoordinate;
varying highp vec2 bottomLeftTextureCoordinate;
varying highp vec2 bottomRightTextureCoordinate;
uniform lowp float threshold;
void main()
{
lowp float bottomColor = texture2D(inputImageTexture, bottomTextureCoordinate).r;
lowp float bottomLeftColor = texture2D(inputImageTexture, bottomLeftTextureCoordinate).r;
lowp float bottomRightColor = texture2D(inputImageTexture, bottomRightTextureCoordinate).r;
lowp vec4 centerColor = texture2D(inputImageTexture, textureCoordinate);
lowp float leftColor = texture2D(inputImageTexture, leftTextureCoordinate).r;
lowp float rightColor = texture2D(inputImageTexture, rightTextureCoordinate).r;
lowp float topColor = texture2D(inputImageTexture, topTextureCoordinate).r;
lowp float topRightColor = texture2D(inputImageTexture, topRightTextureCoordinate).r;
lowp float topLeftColor = texture2D(inputImageTexture, topLeftTextureCoordinate).r;
// Use a tiebreaker for pixels to the left and immediately above this one
lowp float multiplier = 1.0 - step(centerColor.r, topColor);
multiplier = multiplier * (1.0 - step(centerColor.r, topLeftColor));
multiplier = multiplier * (1.0 - step(centerColor.r, leftColor));
multiplier = multiplier * (1.0 - step(centerColor.r, bottomLeftColor));
lowp float maxValue = max(centerColor.r, bottomColor);
maxValue = max(maxValue, bottomRightColor);
maxValue = max(maxValue, rightColor);
maxValue = max(maxValue, topRightColor);
lowp float finalValue = centerColor.r * step(maxValue, centerColor.r) * multiplier;
finalValue = step(threshold, finalValue);
gl_FragColor = vec4(finalValue, finalValue, finalValue, 1.0);
//
// gl_FragColor = vec4((centerColor.rgb * step(maxValue, step(threshold, centerColor.r)) * multiplier), 1.0);
}
);
NSString *const kGPUImageThresholdedNonMaximumSuppressionPackedColorspaceFragmentShaderString = SHADER_STRING
(
uniform sampler2D inputImageTexture;
varying highp vec2 textureCoordinate;
varying highp vec2 leftTextureCoordinate;
varying highp vec2 rightTextureCoordinate;
varying highp vec2 topTextureCoordinate;
varying highp vec2 topLeftTextureCoordinate;
varying highp vec2 topRightTextureCoordinate;
varying highp vec2 bottomTextureCoordinate;
varying highp vec2 bottomLeftTextureCoordinate;
varying highp vec2 bottomRightTextureCoordinate;
uniform lowp float threshold;
uniform highp float texelWidth;
uniform highp float texelHeight;
highp float encodedIntensity(highp vec3 sourceColor)
{
return (sourceColor.b * 256.0 * 256.0 + sourceColor.g * 256.0 + sourceColor.r);
}
void main()
{
highp float bottomColor = encodedIntensity(texture2D(inputImageTexture, bottomTextureCoordinate).rgb);
highp float bottomLeftColor = encodedIntensity(texture2D(inputImageTexture, bottomLeftTextureCoordinate).rgb);
highp float bottomRightColor = encodedIntensity(texture2D(inputImageTexture, bottomRightTextureCoordinate).rgb);
highp float centerColor = encodedIntensity(texture2D(inputImageTexture, textureCoordinate).rgb);
highp float leftColor = encodedIntensity(texture2D(inputImageTexture, leftTextureCoordinate).rgb);
highp float rightColor = encodedIntensity(texture2D(inputImageTexture, rightTextureCoordinate).rgb);
highp float topColor = encodedIntensity(texture2D(inputImageTexture, topTextureCoordinate).rgb);
highp float topRightColor = encodedIntensity(texture2D(inputImageTexture, topRightTextureCoordinate).rgb);
highp float topLeftColor = encodedIntensity(texture2D(inputImageTexture, topLeftTextureCoordinate).rgb);
highp float secondStageColor1 = encodedIntensity(texture2D(inputImageTexture, textureCoordinate + vec2(-2.0 * texelWidth, -2.0 * texelHeight)).rgb);
highp float secondStageColor2 = encodedIntensity(texture2D(inputImageTexture, textureCoordinate + vec2(-2.0 * texelWidth, -1.0 * texelHeight)).rgb);
highp float secondStageColor3 = encodedIntensity(texture2D(inputImageTexture, textureCoordinate + vec2(-2.0 * texelWidth, 0.0)).rgb);
highp float secondStageColor4 = encodedIntensity(texture2D(inputImageTexture, textureCoordinate + vec2(-2.0 * texelWidth, 1.0 * texelHeight)).rgb);
highp float secondStageColor5 = encodedIntensity(texture2D(inputImageTexture, textureCoordinate + vec2(-2.0 * texelWidth, 2.0 * texelHeight)).rgb);
highp float secondStageColor6 = encodedIntensity(texture2D(inputImageTexture, textureCoordinate + vec2(-1.0 * texelWidth, 2.0 * texelHeight)).rgb);
highp float secondStageColor7 = encodedIntensity(texture2D(inputImageTexture, textureCoordinate + vec2(0.0, 2.0 * texelHeight)).rgb);
highp float secondStageColor8 = encodedIntensity(texture2D(inputImageTexture, textureCoordinate + vec2(1.0 * texelWidth, 2.0 * texelHeight)).rgb);
highp float thirdStageColor1 = encodedIntensity(texture2D(inputImageTexture, textureCoordinate + vec2(-1.0 * texelWidth, -2.0 * texelHeight)).rgb);
highp float thirdStageColor2 = encodedIntensity(texture2D(inputImageTexture, textureCoordinate + vec2(0.0, -2.0 * texelHeight)).rgb);
highp float thirdStageColor3 = encodedIntensity(texture2D(inputImageTexture, textureCoordinate + vec2(1.0 * texelWidth, -2.0 * texelHeight)).rgb);
highp float thirdStageColor4 = encodedIntensity(texture2D(inputImageTexture, textureCoordinate + vec2(2.0 * texelWidth, -2.0 * texelHeight)).rgb);
highp float thirdStageColor5 = encodedIntensity(texture2D(inputImageTexture, textureCoordinate + vec2(2.0 * texelWidth, -1.0 * texelHeight)).rgb);
highp float thirdStageColor6 = encodedIntensity(texture2D(inputImageTexture, textureCoordinate + vec2(2.0 * texelWidth, 0.0)).rgb);
highp float thirdStageColor7 = encodedIntensity(texture2D(inputImageTexture, textureCoordinate + vec2(2.0 * texelWidth, 1.0 * texelHeight)).rgb);
highp float thirdStageColor8 = encodedIntensity(texture2D(inputImageTexture, textureCoordinate + vec2(2.0 * texelWidth, 2.0 * texelHeight)).rgb);
// Use a tiebreaker for pixels to the left and immediately above this one
highp float multiplier = 1.0 - step(centerColor, topColor);
multiplier = multiplier * (1.0 - step(centerColor, topLeftColor));
multiplier = multiplier * (1.0 - step(centerColor, leftColor));
multiplier = multiplier * (1.0 - step(centerColor, bottomLeftColor));
multiplier = multiplier * (1.0 - step(centerColor, secondStageColor1));
multiplier = multiplier * (1.0 - step(centerColor, secondStageColor2));
multiplier = multiplier * (1.0 - step(centerColor, secondStageColor3));
multiplier = multiplier * (1.0 - step(centerColor, secondStageColor4));
multiplier = multiplier * (1.0 - step(centerColor, secondStageColor5));
multiplier = multiplier * (1.0 - step(centerColor, secondStageColor6));
multiplier = multiplier * (1.0 - step(centerColor, secondStageColor7));
multiplier = multiplier * (1.0 - step(centerColor, secondStageColor8));
highp float maxValue = max(centerColor, bottomColor);
maxValue = max(maxValue, bottomRightColor);
maxValue = max(maxValue, rightColor);
maxValue = max(maxValue, topRightColor);
maxValue = max(maxValue, thirdStageColor1);
maxValue = max(maxValue, thirdStageColor2);
maxValue = max(maxValue, thirdStageColor3);
maxValue = max(maxValue, thirdStageColor4);
maxValue = max(maxValue, thirdStageColor5);
maxValue = max(maxValue, thirdStageColor6);
maxValue = max(maxValue, thirdStageColor7);
maxValue = max(maxValue, thirdStageColor8);
highp float midValue = centerColor * step(maxValue, centerColor) * multiplier;
highp float finalValue = step(threshold, midValue);
gl_FragColor = vec4(finalValue * centerColor, topLeftColor, topRightColor, topColor);
}
);
#else
NSString *const kGPUImageThresholdedNonMaximumSuppressionFragmentShaderString = SHADER_STRING
(
uniform sampler2D inputImageTexture;
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 float threshold;
void main()
{
float bottomColor = texture2D(inputImageTexture, bottomTextureCoordinate).r;
float bottomLeftColor = texture2D(inputImageTexture, bottomLeftTextureCoordinate).r;
float bottomRightColor = texture2D(inputImageTexture, bottomRightTextureCoordinate).r;
vec4 centerColor = texture2D(inputImageTexture, textureCoordinate);
float leftColor = texture2D(inputImageTexture, leftTextureCoordinate).r;
float rightColor = texture2D(inputImageTexture, rightTextureCoordinate).r;
float topColor = texture2D(inputImageTexture, topTextureCoordinate).r;
float topRightColor = texture2D(inputImageTexture, topRightTextureCoordinate).r;
float topLeftColor = texture2D(inputImageTexture, topLeftTextureCoordinate).r;
// Use a tiebreaker for pixels to the left and immediately above this one
float multiplier = 1.0 - step(centerColor.r, topColor);
multiplier = multiplier * (1.0 - step(centerColor.r, topLeftColor));
multiplier = multiplier * (1.0 - step(centerColor.r, leftColor));
multiplier = multiplier * (1.0 - step(centerColor.r, bottomLeftColor));
float maxValue = max(centerColor.r, bottomColor);
maxValue = max(maxValue, bottomRightColor);
maxValue = max(maxValue, rightColor);
maxValue = max(maxValue, topRightColor);
float finalValue = centerColor.r * step(maxValue, centerColor.r) * multiplier;
finalValue = step(threshold, finalValue);
gl_FragColor = vec4(finalValue, finalValue, finalValue, 1.0);
//
// gl_FragColor = vec4((centerColor.rgb * step(maxValue, step(threshold, centerColor.r)) * multiplier), 1.0);
}
);
NSString *const kGPUImageThresholdedNonMaximumSuppressionPackedColorspaceFragmentShaderString = SHADER_STRING
(
uniform sampler2D inputImageTexture;
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 float threshold;
void main()
{
float bottomColor = texture2D(inputImageTexture, bottomTextureCoordinate).r;
float bottomLeftColor = texture2D(inputImageTexture, bottomLeftTextureCoordinate).r;
float bottomRightColor = texture2D(inputImageTexture, bottomRightTextureCoordinate).r;
vec4 centerColor = texture2D(inputImageTexture, textureCoordinate);
float leftColor = texture2D(inputImageTexture, leftTextureCoordinate).r;
float rightColor = texture2D(inputImageTexture, rightTextureCoordinate).r;
float topColor = texture2D(inputImageTexture, topTextureCoordinate).r;
float topRightColor = texture2D(inputImageTexture, topRightTextureCoordinate).r;
float topLeftColor = texture2D(inputImageTexture, topLeftTextureCoordinate).r;
// Use a tiebreaker for pixels to the left and immediately above this one
float multiplier = 1.0 - step(centerColor.r, topColor);
multiplier = multiplier * (1.0 - step(centerColor.r, topLeftColor));
multiplier = multiplier * (1.0 - step(centerColor.r, leftColor));
multiplier = multiplier * (1.0 - step(centerColor.r, bottomLeftColor));
float maxValue = max(centerColor.r, bottomColor);
maxValue = max(maxValue, bottomRightColor);
maxValue = max(maxValue, rightColor);
maxValue = max(maxValue, topRightColor);
float finalValue = centerColor.r * step(maxValue, centerColor.r) * multiplier;
finalValue = step(threshold, finalValue);
gl_FragColor = vec4(finalValue, finalValue, finalValue, 1.0);
//
// gl_FragColor = vec4((centerColor.rgb * step(maxValue, step(threshold, centerColor.r)) * multiplier), 1.0);
}
);
#endif

复制代码

二.效果演示

使用 GPUImageThresholdedNonMaximumSuppressionFilter 完成图像显示亮度最高的像素,其他为黑,原图如下：

使用 GPUImageThresholdedNonMaximumSuppressionFilter 完成图像显示亮度最高的像素,其他为黑****,效果如下：

三.源码下载

OpenGL ES Demo 下载地址 : IOS – OpenGL ES GPUImage 图像显示亮度最高的像素,其他为黑 GPUImageThresholdedNonMaximumSuppressionFilter

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