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Why editing PNG file result in tEXt disappear?
0
Really need some suggestions here.
I am trying to manually add a tEXt chunk into an existing PNG file just for learning purposes.
While it appeared to be a success, after deliberating editing the image, for e.g. deleting a small portion off the image or rotate it and save, my tEXt chunk is gone. Maybe some part of my code went wrong, some reviews would be appreciated.
byte RAWFILEBYTES = new byte[(int) pngFile.length()];
FileInputStream ins = new FileInputStream(pngFile);
for (int i = 0; i < RAWFILEBYTES.length; i++) {
RAWFILEBYTES[i] = (byte) ins.read();
}
byte size = {(byte) 0x00, (byte) 0x00, (byte) 0x00, (byte) 0x0e};
byte crc32 = new byte[4];
String chunkNameAndKey = "tEXtGreeting";
String value = "hello";
//Declaring size equal to the length of chunk name + key value pair
byte tEXtAndValue = new byte[chunkNameAndKey.getBytes().length + 1 + value.getBytes().length];
//Forming byte array of chunk name and key value pair
System.arraycopy(chunkNameAndKey.getBytes(), 0, tEXtAndValue, 0, chunkNameAndKey.getBytes().length);
tEXtAndValue[chunkNameAndKey.getBytes().length] = (byte) 0x00; //Follow specification key pair value separate by null
System.arraycopy(value.getBytes(), 0, tEXtAndValue, chunkNameAndKey.getBytes().length + 1, value.getBytes().length);
//Calculating checksum comprise of chunk name and value
//E.g. tEXtGreeting[null]hello
Checksum checksum = new CRC32();
checksum.update(tEXtAndValue, 0, tEXtAndValue.length);
//Convert checksum result to 4 bytes according to PNG.
ByteBuffer buffer = ByteBuffer.allocate(Long.BYTES);
buffer.putLong(checksum.getValue());
System.arraycopy(buffer.array(), buffer.array().length - 4, crc32, 0, 4);
//Entire tEXt chunk comprise of size, chunk name, key-value pair and CRC in order.
byte textChunkArr = new byte[4 + tEXtAndValue.length + 4];
System.arraycopy(size, 0, textChunkArr, 0, size.length);
System.arraycopy(tEXtAndValue, 0, textChunkArr, size.length, tEXtAndValue.length);
System.arraycopy(crc32, 0, textChunkArr, size.length + tEXtAndValue.length, crc32.length);
byte byte_array = new byte[RAWFILEBYTES.length + textChunkArr.length];
//Place the text chunk directly before IEND chunk.
System.arraycopy(RAWFILEBYTES, 0, byte_array, 0, RAWFILEBYTES.length - 12);
System.arraycopy(textChunkArr, 0, byte_array, RAWFILEBYTES.length - 12, textChunkArr.length);
System.arraycopy(RAWFILEBYTES, RAWFILEBYTES.length - 12, byte_array, RAWFILEBYTES.length - 12 + textChunkArr.length, 12);
try (FileOutputStream fos = new FileOutputStream("final2_file.png")) {
fos.write(byte_array);
}
In summary, what I'm trying to do, I am creating and insert a tEXt chunk manually directly before IEND chunk.
png
edited Nov 20 '18 at 6:05
Owain Esau
879718
asked Nov 20 '18 at 5:08
JosephJoseph
1124
add a comment |
0
Really need some suggestions here.
I am trying to manually add a tEXt chunk into an existing PNG file just for learning purposes.
While it appeared to be a success, after deliberating editing the image, for e.g. deleting a small portion off the image or rotate it and save, my tEXt chunk is gone. Maybe some part of my code went wrong, some reviews would be appreciated.
byte RAWFILEBYTES = new byte[(int) pngFile.length()];
FileInputStream ins = new FileInputStream(pngFile);
for (int i = 0; i < RAWFILEBYTES.length; i++) {
RAWFILEBYTES[i] = (byte) ins.read();
}
byte size = {(byte) 0x00, (byte) 0x00, (byte) 0x00, (byte) 0x0e};
byte crc32 = new byte[4];
String chunkNameAndKey = "tEXtGreeting";
String value = "hello";
//Declaring size equal to the length of chunk name + key value pair
byte tEXtAndValue = new byte[chunkNameAndKey.getBytes().length + 1 + value.getBytes().length];
//Forming byte array of chunk name and key value pair
System.arraycopy(chunkNameAndKey.getBytes(), 0, tEXtAndValue, 0, chunkNameAndKey.getBytes().length);
tEXtAndValue[chunkNameAndKey.getBytes().length] = (byte) 0x00; //Follow specification key pair value separate by null
System.arraycopy(value.getBytes(), 0, tEXtAndValue, chunkNameAndKey.getBytes().length + 1, value.getBytes().length);
//Calculating checksum comprise of chunk name and value
//E.g. tEXtGreeting[null]hello
Checksum checksum = new CRC32();
checksum.update(tEXtAndValue, 0, tEXtAndValue.length);
//Convert checksum result to 4 bytes according to PNG.
ByteBuffer buffer = ByteBuffer.allocate(Long.BYTES);
buffer.putLong(checksum.getValue());
System.arraycopy(buffer.array(), buffer.array().length - 4, crc32, 0, 4);
//Entire tEXt chunk comprise of size, chunk name, key-value pair and CRC in order.
byte textChunkArr = new byte[4 + tEXtAndValue.length + 4];
System.arraycopy(size, 0, textChunkArr, 0, size.length);
System.arraycopy(tEXtAndValue, 0, textChunkArr, size.length, tEXtAndValue.length);
System.arraycopy(crc32, 0, textChunkArr, size.length + tEXtAndValue.length, crc32.length);
byte byte_array = new byte[RAWFILEBYTES.length + textChunkArr.length];
//Place the text chunk directly before IEND chunk.
System.arraycopy(RAWFILEBYTES, 0, byte_array, 0, RAWFILEBYTES.length - 12);
System.arraycopy(textChunkArr, 0, byte_array, RAWFILEBYTES.length - 12, textChunkArr.length);
System.arraycopy(RAWFILEBYTES, RAWFILEBYTES.length - 12, byte_array, RAWFILEBYTES.length - 12 + textChunkArr.length, 12);
try (FileOutputStream fos = new FileOutputStream("final2_file.png")) {
fos.write(byte_array);
}
In summary, what I'm trying to do, I am creating and insert a tEXt chunk manually directly before IEND chunk.
png
edited Nov 20 '18 at 6:05
Owain Esau
879718
asked Nov 20 '18 at 5:08
JosephJoseph
1124
add a comment |
0
0
0
Really need some suggestions here.
I am trying to manually add a tEXt chunk into an existing PNG file just for learning purposes.
While it appeared to be a success, after deliberating editing the image, for e.g. deleting a small portion off the image or rotate it and save, my tEXt chunk is gone. Maybe some part of my code went wrong, some reviews would be appreciated.
byte RAWFILEBYTES = new byte[(int) pngFile.length()];
FileInputStream ins = new FileInputStream(pngFile);
for (int i = 0; i < RAWFILEBYTES.length; i++) {
RAWFILEBYTES[i] = (byte) ins.read();
}
byte size = {(byte) 0x00, (byte) 0x00, (byte) 0x00, (byte) 0x0e};
byte crc32 = new byte[4];
String chunkNameAndKey = "tEXtGreeting";
String value = "hello";
//Declaring size equal to the length of chunk name + key value pair
byte tEXtAndValue = new byte[chunkNameAndKey.getBytes().length + 1 + value.getBytes().length];
//Forming byte array of chunk name and key value pair
System.arraycopy(chunkNameAndKey.getBytes(), 0, tEXtAndValue, 0, chunkNameAndKey.getBytes().length);
tEXtAndValue[chunkNameAndKey.getBytes().length] = (byte) 0x00; //Follow specification key pair value separate by null
System.arraycopy(value.getBytes(), 0, tEXtAndValue, chunkNameAndKey.getBytes().length + 1, value.getBytes().length);
//Calculating checksum comprise of chunk name and value
//E.g. tEXtGreeting[null]hello
Checksum checksum = new CRC32();
checksum.update(tEXtAndValue, 0, tEXtAndValue.length);
//Convert checksum result to 4 bytes according to PNG.
ByteBuffer buffer = ByteBuffer.allocate(Long.BYTES);
buffer.putLong(checksum.getValue());
System.arraycopy(buffer.array(), buffer.array().length - 4, crc32, 0, 4);
//Entire tEXt chunk comprise of size, chunk name, key-value pair and CRC in order.
byte textChunkArr = new byte[4 + tEXtAndValue.length + 4];
System.arraycopy(size, 0, textChunkArr, 0, size.length);
System.arraycopy(tEXtAndValue, 0, textChunkArr, size.length, tEXtAndValue.length);
System.arraycopy(crc32, 0, textChunkArr, size.length + tEXtAndValue.length, crc32.length);
byte byte_array = new byte[RAWFILEBYTES.length + textChunkArr.length];
//Place the text chunk directly before IEND chunk.
System.arraycopy(RAWFILEBYTES, 0, byte_array, 0, RAWFILEBYTES.length - 12);
System.arraycopy(textChunkArr, 0, byte_array, RAWFILEBYTES.length - 12, textChunkArr.length);
System.arraycopy(RAWFILEBYTES, RAWFILEBYTES.length - 12, byte_array, RAWFILEBYTES.length - 12 + textChunkArr.length, 12);
try (FileOutputStream fos = new FileOutputStream("final2_file.png")) {
fos.write(byte_array);
}
In summary, what I'm trying to do, I am creating and insert a tEXt chunk manually directly before IEND chunk.
png
edited Nov 20 '18 at 6:05
Owain Esau
879718
asked Nov 20 '18 at 5:08
JosephJoseph
1124
Really need some suggestions here.
I am trying to manually add a tEXt chunk into an existing PNG file just for learning purposes.
While it appeared to be a success, after deliberating editing the image, for e.g. deleting a small portion off the image or rotate it and save, my tEXt chunk is gone. Maybe some part of my code went wrong, some reviews would be appreciated.
byte RAWFILEBYTES = new byte[(int) pngFile.length()];
FileInputStream ins = new FileInputStream(pngFile);
for (int i = 0; i < RAWFILEBYTES.length; i++) {
RAWFILEBYTES[i] = (byte) ins.read();
}
byte size = {(byte) 0x00, (byte) 0x00, (byte) 0x00, (byte) 0x0e};
byte crc32 = new byte[4];
String chunkNameAndKey = "tEXtGreeting";
String value = "hello";
//Declaring size equal to the length of chunk name + key value pair
byte tEXtAndValue = new byte[chunkNameAndKey.getBytes().length + 1 + value.getBytes().length];
//Forming byte array of chunk name and key value pair
System.arraycopy(chunkNameAndKey.getBytes(), 0, tEXtAndValue, 0, chunkNameAndKey.getBytes().length);
tEXtAndValue[chunkNameAndKey.getBytes().length] = (byte) 0x00; //Follow specification key pair value separate by null
System.arraycopy(value.getBytes(), 0, tEXtAndValue, chunkNameAndKey.getBytes().length + 1, value.getBytes().length);
//Calculating checksum comprise of chunk name and value
//E.g. tEXtGreeting[null]hello
Checksum checksum = new CRC32();
checksum.update(tEXtAndValue, 0, tEXtAndValue.length);
//Convert checksum result to 4 bytes according to PNG.
ByteBuffer buffer = ByteBuffer.allocate(Long.BYTES);
buffer.putLong(checksum.getValue());
System.arraycopy(buffer.array(), buffer.array().length - 4, crc32, 0, 4);
//Entire tEXt chunk comprise of size, chunk name, key-value pair and CRC in order.
byte textChunkArr = new byte[4 + tEXtAndValue.length + 4];
System.arraycopy(size, 0, textChunkArr, 0, size.length);
System.arraycopy(tEXtAndValue, 0, textChunkArr, size.length, tEXtAndValue.length);
System.arraycopy(crc32, 0, textChunkArr, size.length + tEXtAndValue.length, crc32.length);
byte byte_array = new byte[RAWFILEBYTES.length + textChunkArr.length];
//Place the text chunk directly before IEND chunk.
System.arraycopy(RAWFILEBYTES, 0, byte_array, 0, RAWFILEBYTES.length - 12);
System.arraycopy(textChunkArr, 0, byte_array, RAWFILEBYTES.length - 12, textChunkArr.length);
System.arraycopy(RAWFILEBYTES, RAWFILEBYTES.length - 12, byte_array, RAWFILEBYTES.length - 12 + textChunkArr.length, 12);
try (FileOutputStream fos = new FileOutputStream("final2_file.png")) {
fos.write(byte_array);
}
In summary, what I'm trying to do, I am creating and insert a tEXt chunk manually directly before IEND chunk.
png
png
edited Nov 20 '18 at 6:05
Owain Esau
879718
asked Nov 20 '18 at 5:08
JosephJoseph
1124
edited Nov 20 '18 at 6:05
Owain Esau
879718
asked Nov 20 '18 at 5:08
JosephJoseph
1124
edited Nov 20 '18 at 6:05
Owain Esau
879718
edited Nov 20 '18 at 6:05
Owain Esau
879718
edited Nov 20 '18 at 6:05
Owain Esau
879718
879718
asked Nov 20 '18 at 5:08
JosephJoseph
1124
asked Nov 20 '18 at 5:08
JosephJoseph
1124
asked Nov 20 '18 at 5:08
JosephJoseph
1124
1124
add a comment |
add a comment |
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