Package net.sourceforge.jiu.codecs

Class BMPCodec

  • public class BMPCodec
extends ImageCodec
    A codec to read and write Windows BMP image files.

    Typical file extensions are .bmp and .rle (the latter is only used for compressed files).

    Bounds

    This codec supports the bounds concept for loading and saving.

    Supported BMP types when loading

    • Bilevel, 1 bit per pixel, uncompressed. BMP supports palettes for bilevel images, but the content of that palette is ignored and 0 is considered black and 1 white. Any class implementing BilevelImage can be given to the codec and it will load the image to that object (if the image's resolution is sufficient). If no image object is given to the codec, a new MemoryBilevelImage will be created.
    • Paletted, 4 bits per pixel, uncompressed or RLE4 compression. Both types are loaded to a Paletted8Image object. This requires 50 % more space than is necessary, but there is no dedicated 4 bit image data class in JIU.
    • Paletted, 8 bits per pixel, uncompressed or RLE8 compression. Both types are loaded to a Paletted8Image object.
    • RGB truecolor, 24 bits per pixel, uncompressed. This is loaded to a RGB24Image object.
    There is no support for 16 bpp images or BI_BITFIELDS compression (for lack of test files).

    Supported JIU image data classes when saving to BMP

    • BilevelImage objects are stored as 1 bit per pixel BMP files.
    • Gray8Image and Paletted8Image objects are stored as paletted 8 bits per pixel files. It doesn't really matter how many entries the palette has, the BMP file's palette will always have 256 entries, filled up with zero entries if necessary.
    • RGB24Image objects are stored as 24 bpp BMP files.
    There is no support for compressed BMP files when saving.

    I/O classes

    BMPCodec works with all input and output classes supported by ImageCodec (InputStream, OutputStream, DataInput, DataOutput, RandomAccessFile).

    Problems

    The RLE-compressed BMP files that I could test this codec on seem to have an end-of-line code at the end of every line instead of relying on the decoder to know when it has unpacked enough bytes for a line. Whenever this codec encounters an EOL symbol and has a current column value of 0, the EOL is ignored.

    Usage examples

    Write an image to a BMP file. 
     BMPCodec codec = new BMPCodec();
 codec.setImage(image);
 codec.setFile("out.bmp", CodecMode.SAVE);
 codec.process();
 codec.close();
    Read an image from a BMP file. 
     BMPCodec codec = new BMPCodec();
 codec.setFile("image.bmp", CodecMode.LOAD);
 codec.process();
 codec.close();
 PixelImage image = codec.getImage();
    Since:
    0.7.0
    Author:
    Marco Schmidt