Encoding webp image with transparency cause the no vp8 error. I came to know that if there is no transparent area then there is no error at all and Also the author of the encoder have added the Alpha channle as TODO.
But using the encoder in its original form was throwing errors related to ALPH and ICCP and I saw someone shared the code for ICCP and I used that method for both ALPH and ICCP.
Now the encoder works fine but for images not having Transparency.
This might be the reason:
I used that method for both ALPH and ...
How would I read the ALPH chunks?
Here is the main code where reading takes place.
public class WebpContainerReader {
private final InputStream _inputStream;
private final boolean _debug;
private int _fileSize;
private int _offset;
public WebpContainerReader(InputStream inputStream, boolean debug) {
_inputStream = inputStream;
_debug = debug;
}
public void close() throws IOException {
}
public void readHeader() throws IOException {
byte[] fcc = new byte[4];
read(fcc, 4);
if (!isFourCc(fcc, 'R', 'I', 'F', 'F'))
throw new IOException("Expected RIFF file.");
_fileSize = readUInt32() + 8 - 1;
read(fcc, 4);
if (!isFourCc(fcc, 'W', 'E', 'B', 'P'))
throw new IOException("Expected Webp file.");
}
public WebpChunk read() throws IOException {
byte[] fcc = new byte[4];
if (read(fcc, 4) > 0) {
if (isFourCc(fcc, 'V', 'P', '8', ' '))
return readVp8();
if (isFourCc(fcc, 'V', 'P', '8', 'L'))
return readVp8l();
if (isFourCc(fcc, 'V', 'P', '8', 'X'))
return readVp8x();
if (isFourCc(fcc, 'A', 'N', 'I', 'M'))
return readAnim();
if (isFourCc(fcc, 'A', 'N', 'M', 'F'))
return readAnmf();
if (isFourCc(fcc, 'I', 'C', 'C', 'P'))
return readIccp();
if (isFourCc(fcc, 'A', 'L', 'P', 'H'))
return readAlph();
// calling readAlph() which has same coe as Iccp
throw new IOException(String.format("Not supported FourCC: %c.%c.%c.%c.",
fcc[0], fcc[1], fcc[2], fcc[3]));
}
if (_fileSize != _offset)
throw new IOException(String.format("Header has wrong file size: %d, expected: %d",
_fileSize, _offset));
return null;
}
private WebpChunk readVp8x() throws IOException {
int chunkSize = readUInt32();
if (chunkSize != 10)
throw new IOException("Expected 10 bytes for VP8X.");
WebpChunk chunk = new WebpChunk(WebpChunkType.VP8X);
byte[] flags = new byte[4];
read(flags, 4);
BitSet bs = BitSet.valueOf(flags);
chunk.hasIccp = bs.get(0);
chunk.hasAnim = bs.get(1);
chunk.hasExif = bs.get(2);
chunk.hasXmp = bs.get(3);
chunk.hasAlpha = bs.get(4);
chunk.width = readUInt24();
chunk.height = readUInt24();
debug(String.format("VP8X: size = %dx%d", chunk.width, chunk.height));
return chunk;
}
private byte[] readPayload(int bytes) throws IOException {
byte[] payload = new byte[bytes];
if (read(payload, bytes) != bytes)
throw new IOException("Can not read all bytes.");
return payload;
}
private WebpChunk readVp8() throws IOException {
int chunkSize = readUInt32();
WebpChunk chunk = new WebpChunk(WebpChunkType.VP8);
chunk.isLossless = false;
chunk.payload = readPayload(chunkSize);
debug(String.format("VP8: bytes = %d", chunkSize));
return chunk;
}
private WebpChunk readVp8l() throws IOException {
int chunkSize = readUInt32();
WebpChunk chunk = new WebpChunk(WebpChunkType.VP8L);
chunk.isLossless = true;
chunk.payload = readPayload(chunkSize);
debug(String.format("VP8L: bytes = %d", chunkSize));
return chunk;
}
private WebpChunk readAnim() throws IOException {
int chunkSize = readUInt32();
if (chunkSize != 6)
throw new IOException("Expected 6 bytes for ANIM.");
WebpChunk chunk = new WebpChunk(WebpChunkType.ANIM);
chunk.background = readUInt32();
chunk.loops = readUInt16();
debug(String.format("ANIM: loops = %d", chunk.loops));
return chunk;
}
private WebpChunk readAnmf() throws IOException {
int chunkSize = readUInt32();
WebpChunk chunk = new WebpChunk(WebpChunkType.ANMF);
chunk.x = readUInt24();
chunk.y = readUInt24();
chunk.width = readUInt24();
chunk.height = readUInt24();
chunk.duration = readUInt24();
byte[] flags = new byte[1];
read(flags, 1);
BitSet bs = BitSet.valueOf(flags);
chunk.useAlphaBlending = bs.get(1);
chunk.disposeToBackgroundColor = bs.get(0);
byte[] cch = new byte[4];
read(cch, 4);
if (isFourCc(cch, 'V', 'P', '8', 'L'))
chunk.isLossless = true;
else if (isFourCc(cch, 'V', 'P', '8', ' '))
chunk.isLossless = false;
else
throw new IOException("Not supported ANMF payload.");
readUInt32(); // Payload size.
int payloadSize = chunkSize - 24;
chunk.payload = readPayload(payloadSize);
debug(String.format("ANMF: size = %dx%d, offset = %dx%d, duration = %d, bytes = %d",
chunk.width, chunk.height, chunk.x, chunk.y, chunk.duration, payloadSize));
return chunk;
}
private WebpChunk readIccp() throws IOException {
int chunkSize = readUInt32();
WebpChunk chunk = new WebpChunk(WebpChunkType.VP8);
chunk.isLossless = false;
readPayload(chunkSize);
chunk.payload = null;
debug(String.format("iccp: bytes = %d", chunkSize));
return chunk;
}
private WebpChunk readAlph() throws IOException {
int chunkSize = readUInt32();
WebpChunk chunk = new WebpChunk(WebpChunkType.VP8);
chunk.isLossless = false;
readPayload(chunkSize);
chunk.payload = null;
debug(String.format("alph: bytes = %d", chunkSize));
return chunk;
}
//
private final int read(byte[] buffer, int bytes) throws IOException {
int count = _inputStream.read(buffer, 0, bytes);
_offset += count;
return count;
}
private final int readUint(int bytes) throws IOException {
byte[] b = new byte[] { 0, 0, 0, 0 };
read(b, bytes);
return ByteBuffer.wrap(b, 0, 4).order(ByteOrder.LITTLE_ENDIAN).getInt();
}
private final int readUInt32() throws IOException {
return readUint(4);
}
private final int readUInt24() throws IOException {
return readUint(3);
}
private final int readUInt16() throws IOException {
return readUint(2);
}
private boolean isFourCc(byte[] h, char a, char b, char c, char d) {
return h[0] == a && h[1] == b && h[2] == c && h[3] == d;
}
private void debug(String message) {
if (_debug)
System.out.println(message);
}
}
You can see readAlph() is same as readIccp(). I read specification but could not get how to implement that.
All classes are here on sandbox for ease of access. https://codesandbox.io/s/polished-water-hl32ud?file=/app/muxer/WebpMuxer.java
Please tell me how to fix this. Thanks in advance