image/lib/src/formats/jpeg_decoder.dart

import 'dart:typed_data';

import '../animation.dart';
import '../color.dart';
import '../exif_data.dart';
import '../image.dart';
import '../image_exception.dart';
import '../util/input_buffer.dart';
import 'decode_info.dart';
import 'decoder.dart';
import 'jpeg/jpeg_data.dart';
import 'jpeg/jpeg_info.dart';

/**
 * Decode a jpeg encoded image.
 */
class JpegDecoder extends Decoder {
  JpegInfo info;
  InputBuffer input;

  /**
   * Is the given file a valid JPEG image?
   */
  bool isValidFile(List<int> data) {
    return new JpegData().validate(data);
  }

  DecodeInfo startDecode(List<int> data) {
    input = new InputBuffer(data, bigEndian: true);
    info = new JpegData().readInfo(data);
    return info;
  }

  int numFrames() => info == null ? 0 : info.numFrames;

  Image decodeFrame(int frame) {
    if (input == null) {
      return null;
    }
    JpegData jpeg = new JpegData();
    jpeg.read(input.buffer);

    if (jpeg.frames.length != 1) {
      throw new ImageException('only single frame JPEGs supported');
    }

    Image image = new Image(jpeg.width, jpeg.height, Image.RGB);

    _copyToImage(jpeg, image);

    return image;
  }

  Image decodeImage(List<int> data, {int frame: 0}) {
    JpegData jpeg = new JpegData();
    jpeg.read(data);

    if (jpeg.frames.length != 1) {
      throw new ImageException('only single frame JPEGs supported');
    }

    Image image = new Image(jpeg.width, jpeg.height, Image.RGB);

    _copyToImage(jpeg, image);

    return image;
  }

  Animation decodeAnimation(List<int> data) {
    Image image = decodeImage(data);
    if (image == null) {
      return null;
    }

    Animation anim = new Animation();
    anim.width = image.width;
    anim.height = image.height;
    anim.addFrame(image);

    return anim;
  }

  void _copyToImage(JpegData jpeg, Image imageData) {
    imageData.exif = new ExifData.from(jpeg.exif);

    final width = imageData.width;
    final height = imageData.height;
    final data = jpeg.getData(width, height);
    final components = jpeg.components;

    int i = 0;
    int j = 0;
    switch (components.length) {
      case 1: // Luminance
        for (int y = 0; y < height; y++) {
          for (int x = 0; x < width; x++) {
            int Y = data[i++];
            imageData[j++] = getColor(Y, Y, Y, 255);
          }
        }
        break;
      case 3: // RGB
        for (int y = 0; y < height; y++) {
          for (int x = 0; x < width; x++) {
            int R = data[i++];
            int G = data[i++];
            int B = data[i++];

            int c = getColor(R, G, B, 255);
            imageData[j++] = c;
          }
        }
        break;
      case 4: // CMYK
        for (int y = 0; y < height; y++) {
          for (int x = 0; x < width; x++) {
            int C = data[i++];
            int M = data[i++];
            int Y = data[i++];
            int K = data[i++];

            int R = (C * (K)) >> 8;
            int G = (M * (K)) >> 8;
            int B = (Y * (K)) >> 8;

            imageData[j++] = getColor(R, G, B, 255);
          }
        }
        break;
      default:
        throw 'Unsupported color mode';
    }
  }
}