GPUImageContrastFilter.java

/*
 * Copyright (C) 2012 CyberAgent
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package jp.co.cyberagent.android.gpuimage;

import android.opengl.GLES20;

/**
 * Changes the contrast of the image.<br>
 * <br>
 * contrast value ranges from 0.0 to 4.0, with 1.0 as the normal level
 */
public class GPUImageContrastFilter extends GPUImageFilter {
    public static final String CONTRAST_FRAGMENT_SHADER = "" +
            "varying highp vec2 textureCoordinate;\n" + 
            " \n" + 
            " uniform sampler2D inputImageTexture;\n" + 
            " uniform lowp float contrast;\n" + 
            " \n" + 
            " void main()\n" + 
            " {\n" + 
            "     lowp vec4 textureColor = texture2D(inputImageTexture, textureCoordinate);\n" + 
            "     \n" + 
            "     gl_FragColor = vec4(((textureColor.rgb - vec3(0.5)) * contrast + vec3(0.5)), textureColor.w);\n" + 
            " }";

    private int mContrastLocation;
    private float mContrast;

    public GPUImageContrastFilter() {
        this(1.2f);
    }
    
    public GPUImageContrastFilter(float contrast) {
        super(NO_FILTER_VERTEX_SHADER, CONTRAST_FRAGMENT_SHADER);
        mContrast = contrast;
    }

    @Override
    public void onInit() {
        super.onInit();
        mContrastLocation = GLES20.glGetUniformLocation(getProgram(), "contrast");
    }

    @Override
    public void onInitialized() {
        super.onInitialized();
        setContrast(mContrast);
    }

    public void setContrast(final float contrast) {
        mContrast = contrast;
        setFloat(mContrastLocation, mContrast);
    }
}