PNG Lossless Compression Encoder

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.

• Efficient PNG Encoder
  • Supports 8- and 16-bit greyscale, 24- and 48-bit truecolor, with or without alpha transparency 
  • Outputs complete PNG files compliant with the ISO/IEC 15948 and RFC 2083 standards
  • Optimizes compression ratio by automatically selecting the best prediction filter for each line
  • Implements all four prediction filters, LZ77 with a configurable history window, and Huffman encoding with static tables, and calculates Adler32 and CRC checksums
• Easy to Use and Integrate
  • Run-time programmable image format parameters
  • Automatic program-once encode-many operation
  • AXI4-Stream Interfaces for image and compressed data 
  • AXI-Lite or APB for control and Status register access
  • Interrupts/DMA handshaking signals trigger based on programmable FIFO thresholds
• Throughput & Latency
  • One byte per cycle throughput
    • Higher throughput versions can be made available on request
  • Ultra-low latency:  one image line plus 40 clock cycles
• Synthesis-Time Configuration Options
  • Maximum image resolution and bytes per pixel
  • LZ77 history window size
  • Input & output FIFO depths
• Companion Cores
  • AXI4-SGDMA: DMA engine enabling integration as a memory-mapped peripheral
  • PNG-D: PNG decoder core