private boolean checkJpeg() throws IOException {
byte[] data = new byte[12];
while (true) {
if (read(data, 0, 4) != 4) {
return false;
}
int marker = getShortBigEndian(data, 0);
int size = getShortBigEndian(data, 2);
if ((marker & 0xff00) != 0xff00) {
return false; // not a valid marker
}
if (marker == 0xffe0) { // APPx
if (size < 14) {
// not an APPx header as we know it, skip
skip(size - 2);
continue;
}
if (read(data, 0, 12) != 12) {
return false;
}
final byte[] APP0_ID = {0x4a, 0x46, 0x49, 0x46, 0x00};
if (equals(APP0_ID, 0, data, 0, 5)) {
// System.out.println("data 7=" + data[7]);
if (data[7] == 1) {
setPhysicalWidthDpi(getShortBigEndian(data, 8));
setPhysicalHeightDpi(getShortBigEndian(data, 10));
} else if (data[7] == 2) {
int x = getShortBigEndian(data, 8);
int y = getShortBigEndian(data, 10);
setPhysicalWidthDpi((int) (x * 2.54f));
setPhysicalHeightDpi((int) (y * 2.54f));
}
}
skip(size - 14);
} else if (collectComments && size > 2 && marker == 0xfffe) { // comment
size -= 2;
byte[] chars = new byte[size];
if (read(chars, 0, size) != size) {
return false;
}
String comment = new String(chars, "iso-8859-1");
comment = comment.trim();
addComment(comment);
} else if (marker >= 0xffc0 && marker <= 0xffcf && marker != 0xffc4 && marker != 0xffc8) {
if (read(data, 0, 6) != 6) {
return false;
}
format = FORMAT_JPEG;
bitsPerPixel = (data[0] & 0xff) * (data[5] & 0xff);
progressive = marker == 0xffc2 || marker == 0xffc6 || marker == 0xffca || marker == 0xffce;
width = getShortBigEndian(data, 3);
height = getShortBigEndian(data, 1);
return true;
} else {
skip(size - 2);
}
}
}
private boolean checkPnm(int id) throws IOException {
if (id < 1 || id > 6) {
return false;
}
final int[] PNM_FORMATS = {FORMAT_PBM, FORMAT_PGM, FORMAT_PPM};
format = PNM_FORMATS[(id - 1) % 3];
boolean hasPixelResolution = false;
String s;
while (true) {
s = readLine();
if (s != null) {
s = s.trim();
}
if (s == null || s.length() < 1) {
continue;
}
if (s.charAt(0) == '#') { // comment
if (collectComments && s.length() > 1) {
addComment(s.substring(1));
}
continue;
}
if (!hasPixelResolution) { // split "343 966" into width=343, height=966
int spaceIndex = s.indexOf(' ');
if (spaceIndex == -1) {
return false;
}
String widthString = s.substring(0, spaceIndex);
spaceIndex = s.lastIndexOf(' ');
if (spaceIndex == -1) {
return false;
}
String heightString = s.substring(spaceIndex + 1);
try {
width = Integer.parseInt(widthString);
height = Integer.parseInt(heightString);
} catch (NumberFormatException nfe) {
return false;
}
if (width < 1 || height < 1) {
return false;
}
if (format == FORMAT_PBM) {
bitsPerPixel = 1;
return true;
}
hasPixelResolution = true;
} else {
int maxSample;
try {
maxSample = Integer.parseInt(s);
} catch (NumberFormatException nfe) {
return false;
}
if (maxSample < 0) {
return false;
}
for (int i = 0; i < 25; i++) {
if (maxSample < (1 << (i + 1))) {
bitsPerPixel = i + 1;
if (format == FORMAT_PPM) {
bitsPerPixel *= 3;
}
return true;
}
}
return false;
}
}
}