GPUImageSobelEdgeDetection.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 java.util.ArrayList;
import java.util.List;

/**
 * Applies sobel edge detection on the image.
 */
public class GPUImageSobelEdgeDetection extends GPUImageFilterGroup {

    public static final String SOBEL_EDGE_DETECTION = "" +
            "precision mediump float;\n" + 
            "\n" + 
            "varying vec2 textureCoordinate;\n" + 
            "varying vec2 leftTextureCoordinate;\n" + 
            "varying vec2 rightTextureCoordinate;\n" + 
            "\n" + 
            "varying vec2 topTextureCoordinate;\n" + 
            "varying vec2 topLeftTextureCoordinate;\n" + 
            "varying vec2 topRightTextureCoordinate;\n" + 
            "\n" + 
            "varying vec2 bottomTextureCoordinate;\n" + 
            "varying vec2 bottomLeftTextureCoordinate;\n" + 
            "varying vec2 bottomRightTextureCoordinate;\n" + 
            "\n" + 
            "uniform sampler2D inputImageTexture;\n" + 
            "\n" + 
            "void main()\n" + 
            "{\n" + 
            "    float bottomLeftIntensity = texture2D(inputImageTexture, bottomLeftTextureCoordinate).r;\n" + 
            "    float topRightIntensity = texture2D(inputImageTexture, topRightTextureCoordinate).r;\n" + 
            "    float topLeftIntensity = texture2D(inputImageTexture, topLeftTextureCoordinate).r;\n" + 
            "    float bottomRightIntensity = texture2D(inputImageTexture, bottomRightTextureCoordinate).r;\n" + 
            "    float leftIntensity = texture2D(inputImageTexture, leftTextureCoordinate).r;\n" + 
            "    float rightIntensity = texture2D(inputImageTexture, rightTextureCoordinate).r;\n" + 
            "    float bottomIntensity = texture2D(inputImageTexture, bottomTextureCoordinate).r;\n" + 
            "    float topIntensity = texture2D(inputImageTexture, topTextureCoordinate).r;\n" + 
            "    float h = -topLeftIntensity - 2.0 * topIntensity - topRightIntensity + bottomLeftIntensity + 2.0 * bottomIntensity + bottomRightIntensity;\n" + 
            "    float v = -bottomLeftIntensity - 2.0 * leftIntensity - topLeftIntensity + bottomRightIntensity + 2.0 * rightIntensity + topRightIntensity;\n" + 
            "\n" + 
            "    float mag = length(vec2(h, v));\n" + 
            "\n" + 
            "    gl_FragColor = vec4(vec3(mag), 1.0);\n" + 
            "}";

    public GPUImageSobelEdgeDetection() {
        super(createFilters());
    }

    private static List<GPUImageFilter> createFilters() {
        List<GPUImageFilter> filters = new ArrayList<GPUImageFilter>(2);
        filters.add(new GPUImageGrayscaleFilter());
        filters.add(new GPUImage3x3TextureSamplingFilter(SOBEL_EDGE_DETECTION));
        return filters;
    }

    public void setLineSize(final float size) {
        ((GPUImage3x3TextureSamplingFilter) getFilters().get(1)).setLineSize(size);
    }
}