def writeIHDR(mem: ByteArray, width: int, height: int, bits: int,
colors: int):
chunk = ByteArray()
chunk.writeUnsignedInt(0x49484452)
chunk.writeUnsignedInt(width)
chunk.writeUnsignedInt(height)
chunk.writeByte(bits)
chunk.writeByte(colors)
chunk.writeByte(0x00)
chunk.writeByte(0x00)
chunk.writeByte(0x00)
PNGEncoder.writeChunk(mem, chunk)
def writeSignature(mem: ByteArray):
mem.writeUnsignedInt(0x89504E47)
mem.writeUnsignedInt(0x0D0A1A0A)
def writeChunk(mem: ByteArray, chunk: ByteArray):
mem.writeUnsignedInt(len(chunk) - 4)
mem.writeByteArray(chunk)
mem.writeUnsignedInt(CRC32.hashBytes(chunk))
