OpengGL Es (亮度+ 对比度 + 饱和度 )

变量声明 (GLES 语法)

precision mediump float;
varying highp vec2 textureCoordinate;
uniform sampler2D inputTexture;

//亮度
uniform lowp float brightness;
//对比度
uniform lowp float contrast;

//饱和度
uniform lowp float saturation;
// Values from \\\"Graphics Shaders: Theory and Practice\\\" by Bailey and Cunningham
const mediump vec3 luminanceWeighting = vec3(0.2125, 0.7154, 0.0721);

1.亮度调整

lowp vec4 textureColor = texture2D(inputTexture, textureCoordinate);
gl_FragColor = vec4((textureColor.rgb + vec3(brightness)), textureColor.w);

获取handle

 mBrightnessHandle = GLES20.glGetUniformLocation(mProgramId, "brightness");

赋值 (-1.0 to 1.0, 默认为0.0f)

GLES20.glUniform1f(mBrightnessHandle, 0.0f);

2.对比度

lowp vec4 textureColor = texture2D(inputTexture, textureCoordinate);
 gl_FragColor = vec4((textureColor.rgb - vec3(0.5)) *  contrast + vec3(0.5), textureColor.w);

获取handle

  mContrastHandle = GLES20.glGetUniformLocation(mProgramId, "contrast");

赋值 ( 0.0 ~ 4.0, 默认1.0f)

  GLES20.glUniform1f(mContrastHandle, 1.0f);

3.饱和度

 lowp vec4 textureColor = texture2D(inputTexture, textureCoordinate);
 lowp vec3 greyScaleColor = vec3(dot(contrastColor.rgb, luminanceWeighting));
 gl_FragColor = vec4(mix(greyScaleColor, contrastColor.rgb, saturation), textureColor.w);

获取handle

  mSaturationHandle = GLES30.glGetUniformLocation(mProgramId, "saturation");

赋值(0.0 ~ 2.0之间 默认1.0f)

  GLES20.glUniform1f(mSaturationHandle, mSaturationValue);

如果想一起合并使用同一个fragment_shader，可以这样弄

void main()
{
    //亮度
    lowp vec3 brightnessColor  = textureColor.rgb + vec3(brightness);

    //对比度
    lowp vec3 contrastColor = (brightnessColor.rgb - vec3(0.5)) * contrast + vec3(0.5);

    //饱和度
    lowp vec3 greyScaleColor = vec3(dot(contrastColor.rgb, luminanceWeighting));
    gl_FragColor = vec4(mix(greyScaleColor, contrastColor.rgb, saturation), textureColor.w);
}