Method get_all_idat_data

png.py:207–242

Collect every IDAT chunk, for there may be more than one of them, and then decompress it. After that, separate them by row. Return a list [b'...', ...] What's worth noting is that the first byte of every row represent the filter type instead of pixel data

(self)

        

    def get_all_idat_data(self) -> list:
        """
        Collect every IDAT chunk, for there may be more than one of them, and then 
        decompress it. After that, separate them by row.
        Return a list [b'...', ...]
        What's worth noting is that the first byte of every row represent the filter 
        type instead of pixel data
        """
        # Identify all starting indices of idat chucks since there can be multiple of them
        idat_chunks_indices = []
        start_finding_index = 0
        for _ in range(self.bin.count(b'IDAT')):
            idat_chunks_indices.append(self.bin.index(b'IDAT', start_finding_index) - 4)
            start_finding_index = (idat_chunks_indices[-1] + 
                                   Png.get_chunk_length(self.bin, idat_chunks_indices[-1]) +
                                   8)
        # Check crc
        if self.crc == True:
            for idat_chunk_index in idat_chunks_indices:
                Png.check_crc(self.bin, idat_chunk_index)
        # Merge all chunks into one bytes
        idat_data = b''
        for idat_chunk_index in idat_chunks_indices:
            idat_data += self.bin[idat_chunk_index + 8 :
                                  idat_chunk_index + 8 +
                                  Png.get_chunk_length(self.bin,idat_chunk_index)]
        # Decompress (Huffman & LZSS)
        self.idat_data = zlib.decompress(idat_data)

        # Store the data as rows [b'...', b'...', ...]
        rows = []
        row_length = ceil(self.width * self.channels * self.bit_depth / 8 + 1)
        for row_num in range(self.height):
            rows.append(self.idat_data[row_num * row_length:(row_num + 1) * row_length])

        return rows

                 
    def defilter(self, rows:list,) -> list: