Common.MatDefs.Post.ContrastAdjustment15.frag Maven / Gradle / Ivy

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/*
 * Used by ContrastAdjustment.j3md to adjust the color channels.
 *
 * First, the input range is normalized to upper and lower limits.
 * Then a power law is applied, using the exponent for each channel.
 * Finally, the output value is scaled linearly, using the scaling factor for each channel.
 *
 * Supports glsl150 and glsl150+ including android GLES glsl300, glsl310 and glsl320.
 */

#import "Common/ShaderLib/GLSLCompat.glsllib"
#import "Common/ShaderLib/MultiSample.glsllib"

//constant inputs from java source
uniform float m_redChannelExponent;
uniform float m_greenChannelExponent;
uniform float m_blueChannelExponent;

//final scale values
uniform float m_redChannelScale;
uniform float m_greenChannelScale;
uniform float m_blueChannelScale;

//input range
uniform float m_lowerLimit;
uniform float m_upperLimit;

//container for the input from post15.vert
uniform COLORTEXTURE m_Texture;

//varying input from post15.vert vertex shader
in vec2 texCoord;

//the output color
out vec4 fragColor;

void main() {
    //get the color from a 2d sampler.
    vec4 color = texture2D(m_Texture, texCoord);

    //apply the color transfer function.

    //1) adjust the channels input range
    color.rgb = (color.rgb - vec3(m_lowerLimit)) / (vec3(m_upperLimit) - vec3(m_lowerLimit));

    // avoid negative levels
    color.r = max(color.r, 0.0);
    color.g = max(color.g, 0.0);
    color.b = max(color.b, 0.0);

    //2) apply transfer functions on different channels.
    color.r = pow(color.r, m_redChannelExponent);
    color.g = pow(color.g, m_greenChannelExponent);
    color.b = pow(color.b, m_blueChannelExponent);

    //3) scale the output levels
    color.r = color.r * m_redChannelScale;
    color.b = color.b * m_blueChannelScale;
    color.g = color.g * m_greenChannelScale;

    //4) process the textures colors.
    fragColor = color;
}