content: /*
   * 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();
          addFilter(new GPUImageGrayscaleFilter());
          addFilter(new GPUImage3x3TextureSamplingFilter(SOBEL_EDGE_DETECTION));
      }
  
      public void setLineSize(final float size) {
          ((GPUImage3x3TextureSamplingFilter) getFilters().get(1)).setLineSize(size);
      }
  }
  