/**
* Loads PNG files and returns the result as an int[][]. The only PNG formats permitted are those
* with up to 256 grays (including simple black and white) or indexed colors from an up to
* 256-sized color table. Each integer value represents the gray level or the color table index
* value of the pixel. The Y dimension is not flipped.
*/
public static int[][] loadPNGFile(InputStream str) throws IOException {
// read the bytes into a byte array
BufferedInputStream stream = new BufferedInputStream(str);
ArrayList list = new ArrayList();
int count = 0;
while (true) {
byte[] buffer = new byte[16384 * 16];
int len = stream.read(buffer);
if (len <= 0) // all done
break;
else if (len < buffer.length) {
byte[] buf2 = new byte[len];
System.arraycopy(buffer, 0, buf2, 0, len);
buffer = buf2;
}
count += len;
list.add(buffer);
}
byte[] data = new byte[count];
int cur = 0;
for (int i = 0; i < list.size(); i++) {
byte[] b = (byte[]) (list.get(i));
System.arraycopy(b, 0, data, cur, b.length);
cur += b.length;
}
// Next convert the byte array to a buffered image
BufferedImage image = ((ToolkitImage) (new ImageIcon(data).getImage())).getBufferedImage();
// Is the color model something we can use?
int type = image.getType();
if (type == BufferedImage.TYPE_BYTE_BINARY || type == BufferedImage.TYPE_BYTE_GRAY) {
int w = image.getWidth();
int h = image.getHeight();
int[][] result = new int[w][h];
// obviously this could be done more efficiently
for (int i = 0; i < w; i++)
for (int j = 0; j < h; j++) result[i][j] = (image.getRGB(i, j) & 0xFF);
return result;
} else if (type == BufferedImage.TYPE_BYTE_INDEXED) {
Raster raster = image.getRaster();
if (raster.getTransferType() != DataBuffer.TYPE_BYTE) // uh oh
throw new IOException("Input Stream must contain an image with byte data if indexed.");
byte[] pixel = new byte[1];
int w = image.getWidth();
int h = image.getHeight();
int[][] result = new int[w][h];
// obviously this could be done more efficiently
for (int i = 0; i < w; i++)
for (int j = 0; j < h; j++) {
result[i][j] = ((byte[]) (raster.getDataElements(i, j, pixel)))[0];
if (result[i][j] < 0) result[i][j] += 256;
}
return result;
}
// else if (type == TYPE_USHORT_GRAY) // at present we don't handle shorts
// {
// }
else
throw new IOException(
"Input Stream must contain a binary, byte-sized grayscale, or byte-sized indexed color scheme: "
+ image);
}
