content: /*
   * Copyright (C) 2019 Adaptech s.r.o., Robert Pösel
   * Copyright (C) 2014 Robert Theis
   *
   * 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 com.googlecode.leptonica.android;
  
  import java.lang.annotation.Retention;
  
  import androidx.annotation.IntDef;
  
  import static java.lang.annotation.RetentionPolicy.SOURCE;
  
  /**
   * Edge detection.
   */
  @SuppressWarnings("WeakerAccess")
  public class Edge {
  	static {
  		System.loadLibrary("jpeg");
  		System.loadLibrary("pngx");
  		System.loadLibrary("leptonica");
  	}
  
  	// Edge orientation flags
  	@Retention(SOURCE)
  	@IntDef({L_HORIZONTAL_EDGES, L_VERTICAL_EDGES, L_ALL_EDGES})
  	public @interface EdgeOrientationFlag {
  	}
  
  	/**
  	 * Filters for horizontal edges
  	 */
  	public static final int L_HORIZONTAL_EDGES = 0;
  
  	/**
  	 * Filters for vertical edges
  	 */
  	public static final int L_VERTICAL_EDGES = 1;
  
  	/**
  	 * Filters for all edges
  	 */
  	public static final int L_ALL_EDGES = 2;
  
  	/**
  	 * Performs a Sobel edge detecting filter.
  	 * <p>
  	 * To use both the vertical and horizontal filters, set the orientation
  	 * flag to L_ALL_EDGES; this sums the abs. value of their outputs,
  	 * clipped to 255.
  	 * <p>
  	 * Notes:
  	 * <ol>
  	 * <li> Invert pixd to see larger gradients as darker (grayscale).
  	 * <li> To generate a binary image of the edges, threshold the result
  	 * using pixThresholdToBinary().  If the high edge values are to be fg (1),
  	 * invert after running pixThresholdToBinary().
  	 * <li> Label the pixels as follows:
  	 * <p>         1    4    7
  	 * <p>         2    5    8
  	 * <p>         3    6    9
  	 * <p>
  	 * Read the data incrementally across the image and unroll the loop.
  	 * <li> This runs at about 45 Mpix/sec on a 3 GHz processor.
  	 * </ol>
  	 *
  	 * @param pixs       Source pix (8 bpp; no colormap)
  	 * @param orientFlag Edge orientation flag (L_HORIZONTAL_EDGES,
  	 *                   L_VERTICAL_EDGES, L_ALL_EDGES)
  	 * @return a new Pix image (8bpp, edges are brighter), or null on error
  	 */
  	public static Pix pixSobelEdgeFilter(Pix pixs, @EdgeOrientationFlag int orientFlag) {
  		if (pixs == null)
  			throw new IllegalArgumentException("Source pix must be non-null");
  		if (pixs.getDepth() != 8)
  			throw new IllegalArgumentException("Source pix depth must be 8bpp");
  		if (orientFlag < 0 || orientFlag > 2)
  			throw new IllegalArgumentException("Invalid orientation flag");
  
  		long nativePix = nativePixSobelEdgeFilter(pixs.getNativePix(),
  				orientFlag);
  
  		if (nativePix == 0)
  			throw new RuntimeException("Failed to perform Sobel edge filter on image");
  
  		return new Pix(nativePix);
  	}
  
  	// ***************
  	// * NATIVE CODE *
  	// ***************
  
  	private static native long nativePixSobelEdgeFilter(long nativePix, int orientFlag);
  }
  