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;
  
  /**
   * Converts video to look like a sketch.
   * This is just the Sobel edge detection filter with the colors inverted.
   */
  public class GPUImageSketchFilter extends GPUImageFilterGroup {
      public static final String SKETCH_FRAGMENT_SHADER = "" +
              "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 = 1.0 - length(vec2(h, v));\n" +
              "\n" +
              "gl_FragColor = vec4(vec3(mag), 1.0);\n" +
              "}\n";
  
      public GPUImageSketchFilter() {
          super();
          addFilter(new GPUImageGrayscaleFilter());
          addFilter(new GPUImage3x3TextureSamplingFilter(SKETCH_FRAGMENT_SHADER));
      }
  }
  