The PNG-E core implements a lossless image compression engine compliant with the Portable Network Graphics (PNG) file format specified in the ISO/IEC 15948 and RFC 2083 standards.
The encoder core can compress greyscale or color (RGB) images, with 8 and 16 bits per color, with or without alpha transparency, and produces complete PNG files. It exhibits excellent compression efficiency thanks to its ability to automatically and dynamically choose the optimal prediction filter per line. It supports all four prediction filters, LZ77 with a configurable History Window, and Static Huffman tables, and computes CRC and Adler32 checksums as provisioned by the standard. The core does not currently support the interlaced mode, Dynamic Huffman tables, and images with less than 8 bits per color, but these can be added on request.
The easy-to-use PNG-E core interfaces to the system via standardized AMBA® interfaces: it accepts images and outputs compressed data via AXI4-Stream interfaces and provides access to its control and status registers via a 32-bit APB interface. After its registers are programmed with the image dimensions and color format, the core can encode an arbitrary number of images without requiring any assistance or action from the system. The core provides one interrupt signal per direction to facilitate integration with a DMA engine. These interrupts are asserted when the input or output FIFO occupancy reaches a run-time programmable threshold.
