A decoder for Windows bitmap (.BMP) files
/*
* BMPLoader.
*
* JavaZOOM : jlgui@javazoom.net
* http://www.javazoom.net
*
*-----------------------------------------------------------------------
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU Library General Public License as published
* by the Free Software Foundation; either version 2 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU Library General Public License for more details.
*
* You should have received a copy of the GNU Library General Public
* License along with this program; if not, write to the Free Software
* Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
*----------------------------------------------------------------------
*/
import java.awt.Image;
import java.awt.Toolkit;
import java.awt.image.ColorModel;
import java.awt.image.IndexColorModel;
import java.awt.image.MemoryImageSource;
import java.io.IOException;
import java.io.InputStream;
/**
* A decoder for Windows bitmap (.BMP) files.
* Compression not supported.
*/
public class BMPLoader
{
private InputStream is;
private int curPos = 0;
private int bitmapOffset; // starting position of image data
private int width; // image width in pixels
private int height; // image height in pixels
private short bitsPerPixel; // 1, 4, 8, or 24 (no color map)
private int compression; // 0 (none), 1 (8-bit RLE), or 2 (4-bit RLE)
private int actualSizeOfBitmap;
private int scanLineSize;
private int actualColorsUsed;
private byte r[], g[], b[]; // color palette
private int noOfEntries;
private byte[] byteData; // Unpacked data
private int[] intData; // Unpacked data
public BMPLoader()
{
}
public Image getBMPImage(InputStream stream) throws Exception
{
read(stream);
return Toolkit.getDefaultToolkit().createImage(getImageSource());
}
protected int readInt() throws IOException
{
int b1 = is.read();
int b2 = is.read();
int b3 = is.read();
int b4 = is.read();
curPos += 4;
return ((b4 << 24) + (b3 << 16) + (b2 << 8) + (b1 << 0));
}
protected short readShort() throws IOException
{
int b1 = is.read();
int b2 = is.read();
curPos += 4;
return (short) ((b2 << 8) + b1);
}
protected void getFileHeader() throws IOException, Exception
{
// Actual contents (14 bytes):
short fileType = 0x4d42;// always "BM"
int fileSize; // size of file in bytes
short reserved1 = 0; // always 0
short reserved2 = 0; // always 0
fileType = readShort();
if (fileType != 0x4d42) throw new Exception("Not a BMP file"); // wrong file type
fileSize = readInt();
reserved1 = readShort();
reserved2 = readShort();
bitmapOffset = readInt();
}
protected void getBitmapHeader() throws IOException
{
// Actual contents (40 bytes):
int size; // size of this header in bytes
short planes; // no. of color planes: always 1
int sizeOfBitmap; // size of bitmap in bytes (may be 0: if so, calculate)
int horzResolution; // horizontal resolution, pixels/meter (may be 0)
int vertResolution; // vertical resolution, pixels/meter (may be 0)
int colorsUsed; // no. of colors in palette (if 0, calculate)
int colorsImportant; // no. of important colors (appear first in palette) (0 means all are important)
boolean topDown;
int noOfPixels;
size = readInt();
width = readInt();
height = readInt();
planes = readShort();
bitsPerPixel = readShort();
compression = readInt();
sizeOfBitmap = readInt();
horzResolution = readInt();
vertResolution = readInt();
colorsUsed = readInt();
colorsImportant = readInt();
topDown = (height < 0);
noOfPixels = width * height;
// Scan line is padded with zeroes to be a multiple of four bytes
scanLineSize = ((width * bitsPerPixel + 31) / 32) * 4;
if (sizeOfBitmap != 0) actualSizeOfBitmap = sizeOfBitmap;
else
// a value of 0 doesn't mean zero - it means we have to calculate it
actualSizeOfBitmap = scanLineSize * height;
if (colorsUsed != 0) actualColorsUsed = colorsUsed;
else
// a value of 0 means we determine this based on the bits per pixel
if (bitsPerPixel < 16) actualColorsUsed = 1 << bitsPerPixel;
else actualColorsUsed = 0; // no palette
}
protected void getPalette() throws IOException
{
noOfEntries = actualColorsUsed;
//IJ.write("noOfEntries: " + noOfEntries);
if (noOfEntries > 0)
{
r = new byte[noOfEntries];
g = new byte[noOfEntries];
b = new byte[noOfEntries];
int reserved;
for (int i = 0; i < noOfEntries; i++)
{
b[i] = (byte) is.read();
g[i] = (byte) is.read();
r[i] = (byte) is.read();
reserved = is.read();
curPos += 4;
}
}
}
protected void unpack(byte[] rawData, int rawOffset, int[] intData, int intOffset, int w)
{
int j = intOffset;
int k = rawOffset;
int mask = 0xff;
for (int i = 0; i < w; i++)
{
int b0 = (((int) (rawData[k++])) & mask);
int b1 = (((int) (rawData[k++])) & mask) << 8;
int b2 = (((int) (rawData[k++])) & mask) << 16;
intData[j] = 0xff000000 | b0 | b1 | b2;
j++;
}
}
protected void unpack(byte[] rawData, int rawOffset, int bpp, byte[] byteData, int byteOffset, int w) throws Exception
{
int j = byteOffset;
int k = rawOffset;
byte mask;
int pixPerByte;
switch (bpp)
{
case 1:
mask = (byte) 0x01;
pixPerByte = 8;
break;
case 4:
mask = (byte) 0x0f;
pixPerByte = 2;
break;
case 8:
mask = (byte) 0xff;
pixPerByte = 1;
break;
default:
throw new Exception("Unsupported bits-per-pixel value");
}
for (int i = 0;;)
{
int shift = 8 - bpp;
for (int ii = 0; ii < pixPerByte; ii++)
{
byte br = rawData[k];
br >>= shift;
byteData[j] = (byte) (br & mask);
//System.out.println("Setting byteData[" + j + "]=" + Test.byteToHex(byteData[j]));
j++;
i++;
if (i == w) return;
shift -= bpp;
}
k++;
}
}
protected int readScanLine(byte[] b, int off, int len) throws IOException
{
int bytesRead = 0;
int l = len;
int r = 0;
while (len > 0)
{
bytesRead = is.read(b, off, len);
if (bytesRead == -1) return r == 0 ? -1 : r;
if (bytesRead == len) return l;
len -= bytesRead;
off += bytesRead;
r += bytesRead;
}
return l;
}
protected void getPixelData() throws IOException, Exception
{
byte[] rawData; // the raw unpacked data
// Skip to the start of the bitmap data (if we are not already there)
long skip = bitmapOffset - curPos;
if (skip > 0)
{
is.skip(skip);
curPos += skip;
}
int len = scanLineSize;
if (bitsPerPixel > 8) intData = new int[width * height];
else byteData = new byte[width * height];
rawData = new byte[actualSizeOfBitmap];
int rawOffset = 0;
int offset = (height - 1) * width;
for (int i = height - 1; i >= 0; i--)
{
int n = readScanLine(rawData, rawOffset, len);
if (n < len) throw new Exception("Scan line ended prematurely after " + n + " bytes");
if (bitsPerPixel > 8)
{
// Unpack and create one int per pixel
unpack(rawData, rawOffset, intData, offset, width);
}
else
{
// Unpack and create one byte per pixel
unpack(rawData, rawOffset, bitsPerPixel, byteData, offset, width);
}
rawOffset += len;
offset -= width;
}
}
public void read(InputStream is) throws IOException, Exception
{
this.is = is;
getFileHeader();
getBitmapHeader();
if (compression != 0) throw new Exception("BMP Compression not supported");
getPalette();
getPixelData();
}
public MemoryImageSource getImageSource()
{
ColorModel cm;
MemoryImageSource mis;
if (noOfEntries > 0)
{
// There is a color palette; create an IndexColorModel
cm = new IndexColorModel(bitsPerPixel, noOfEntries, r, g, b);
}
else
{
// There is no palette; use the default RGB color model
cm = ColorModel.getRGBdefault();
}
// Create MemoryImageSource
if (bitsPerPixel > 8)
{
// use one int per pixel
mis = new MemoryImageSource(width, height, cm, intData, 0, width);
}
else
{
// use one byte per pixel
mis = new MemoryImageSource(width, height, cm, byteData, 0, width);
}
return mis; // this can be used by JComponent.createImage()
}
}
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