PNG to DJVU Converter

PNG (Portable Network Graphics) is a lossless raster image format developed by the PNG Development Group and published as a W3C Recommendation on October 1, 1996, created as a patent-free replacement for GIF after the Unisys LZW patent controversy. PNG uses a two-stage compression pipeline: a prediction filter selects the optimal per-row preprocessing (none, sub, up, average, or Paeth), then DEFLATE compression encodes the filtered data. The format supports rich color modes — 1/2/4/8/16-bit grayscale, 8/16-bit per channel true color, and indexed color with palettes up to 256 entries — all with optional alpha transparency ranging from a single transparent color to a full per-pixel alpha channel with 256 or 65536 levels. PNG also stores gamma correction, ICC color profiles, text metadata, and suggested background color. One advantage is lossless compression with transparency — PNG preserves every pixel exactly while supporting smooth semi-transparent edges, making it the standard format for web graphics, UI elements, logos, screenshots, and any image where artifacts or color shifts are unacceptable. Universal support is another core strength: every web browser, operating system, image editor, and programming library handles PNG natively. The format has proven remarkably durable — after nearly three decades, PNG remains the default lossless web image format. While newer formats like WebP and AVIF offer better compression, PNG's combination of lossless quality, full transparency, and absolute ubiquity keeps it indispensable.