CUSTOM.md

Define custom configuration

1. Add new shader file to list of assets in pubspec.yaml

# The following section is specific to Flutter packages.
flutter:
  uses-material-design: true
  assets:
    - shaders/Custom.glsl

Shader must contain two variable

varying highp vec2 textureCoordinate; // texture coordinates

uniform sampler2D inputImageTexture; // input video frame

If you need to allow your function to be part of shader's bunch add vec4 processColor(vec4 sourceColor) function

vec4 processColor(vec4 sourceColor){
   ...
}

void main() {
    highp vec4 textureColor = texture2D(inputImageTexture, textureCoordinate);

    gl_FragColor = processColor(textureColor);
}

2. Create class extended from GPUFilterConfiguration and define inputs of filter

uniform	Parameter
sampler2D	GLBitmapParameter
vec3	GLColorParameter
vec3	GLVec3Parameter
mat3	GLMat3Parameter
mat4	GLMat4Parameter
vec2	GLPointParameter
float	GLSliderFloatParameter
float	GLFloatParameter
float	GLIntParameter
float	GLBoolParameter

Example

Let's update Brightness shader to apple value -0.2 and save it to shaders/CustomBrightness.glsl

precision mediump float;
varying vec2 textureCoordinate;

uniform lowp sampler2D inputImageTexture;
uniform lowp float inputBrightness;

vec4 processColor(vec4 sourceColor){
    return vec4((sourceColor.rgb + vec3(inputBrightness - 0.2)), sourceColor.w);
}

void main()
{
    lowp vec4 textureColor = texture2D(inputImageTexture, textureCoordinate);

    gl_FragColor = processColor(textureColor);
}

class GPUCustomBrightnessConfiguration extends GPUFilterConfiguration {
  final NumberParameter _brightness;

  GPUCustomBrightnessConfiguration()
      : _brightness = GLSliderFloatParameter(
    'inputBrightness', // uniform name
    'Brightness', // display name
    0, // default value
    min: -1, // minimum value
    max: 1, // maximum value
  ),
        super('CustomBrightness', // glsl file name
          fragmentShadersPath: 'shaders' // assets location
      );

  // custom setter (optional)
  set brightness(double value) {
    _brightness.value = value;
  }

  // enlist all parameters
  @override
  List<ConfigurationParameter> get parameters => [_brightness];
}