/*
 * Copyright 2009 ZXing authors
 *
 * 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.google.zxing.client.j2me;

import com.google.zxing.LuminanceSource;

import javax.microedition.lcdui.Image;

/**
 * A LuminanceSource based on Java ME's Image class. It does not support cropping or rotation.
 *
 * @author dswitkin@google.com (Daniel Switkin)
 * @author Sean Owen
 */
public final class LCDUIImageLuminanceSource extends LuminanceSource {

  private final Image image;
  private int[] rgbData;

  public LCDUIImageLuminanceSource(Image image) {
    super(image.getWidth(), image.getHeight());
    this.image = image;
  }

  // Instead of multiplying by 306, 601, 117, we multiply by 256, 512, 256, so that
  // the multiplies can be implemented as shifts.
  //
  // Really, it's:
  //
  // return ((((pixel >> 16) & 0xFF) << 8) +
  //         (((pixel >>  8) & 0xFF) << 9) +
  //         (( pixel        & 0xFF) << 8)) >> 10;
  //
  // That is, we're replacing the coefficients in the original with powers of two,
  // which can be implemented as shifts, even though changing the coefficients slightly
  // alters the conversion. The difference is not significant for our purposes.
  public byte[] getRow(int y, byte[] row) {
    if (y < 0 || y >= getHeight()) {
      throw new IllegalArgumentException("Requested row is outside the image: " + y);
    }
    int width = getWidth();
    if (row == null || row.length < width) {
      row = new byte[width];
    }

    if (rgbData == null || rgbData.length < width) {
      rgbData = new int[width];
    }
    image.getRGB(rgbData, 0, width, 0, y, width, 1);
    for (int x = 0; x < width; x++) {
      int pixel = rgbData[x];
      int luminance = (((pixel & 0x00FF0000) >> 16) +
                       ((pixel & 0x0000FF00) >>  7) +
                        (pixel & 0x000000FF       )) >> 2;
      row[x] = (byte) luminance;
    }
    return row;
  }

  public byte[] getMatrix() {
    int width = getWidth();
    int height = getHeight();
    int area = width * height;
    byte[] matrix = new byte[area];

    int[] rgb = new int[area];
    image.getRGB(rgb, 0, width, 0, 0, width, height);
    for (int y = 0; y < height; y++) {
      int offset = y * width;
      for (int x = 0; x < width; x++) {
        int pixel = rgb[offset + x];
        int luminance = (((pixel & 0x00FF0000) >> 16) +
                         ((pixel & 0x0000FF00) >>  7) +
                          (pixel & 0x000000FF       )) >> 2;
        matrix[offset + x] = (byte) luminance;
      }
    }
    return matrix;
  }

}