DNG to PCX Converter

Encoding: the DNG uses lossless (or lossy) JPEG-compressed sensor data, plus optional JPEG previews; PCX uses byte-wise run-length encoding, and the download is a run-length encoded PCX: 8-bit indexed when the image has 256 colours or fewer, otherwise 24-bit RGB.

Bit depth: 8 to 16 bits per channel in the DNG; PCX allows 1, 2, 4 or 8 bits per pixel with a palette, or 24-bit as three 8-bit planes, and the PCX written here has 8-bit indexed or 24-bit RGB. The raw data's 12 to 16 bits are not used: the embedded 8-bit preview is converted.

Colour: camera RGB plus the colour matrices that map it to XYZ (demosaiced linear RGB in a Linear DNG) in the DNG; PCX supports a 16 or 256-colour palette, or 24-bit RGB, written here as 8-bit sRGB.

Metadata: the DNG can carry EXIF, XMP and DNG tags for colour matrices, calibration and lens corrections; PCX can carry only a 128-byte header with the resolution, but nothing is copied across.

DNG is Adobe's openly documented raw format. Some cameras and phones record it directly, Adobe DNG Converter turns other brands' raw files into it, and a Linear DNG holds already-demosaiced RGB that raw editors treat like any other raw file.

DNG is built on TIFF/EP. The raw image sits in a sub-IFD marked as the main image, with tags for black and white levels, colour matrices and the colour filter pattern; a Linear DNG (PhotometricInterpretation 34892) stores demosaiced RGB instead of a mosaic. Previews are optional, and Adobe DNG Converter can write a medium (1024 px), full-size or no preview.

DNG files usually come from Leica, Pentax and Ricoh cameras, DJI drones, Google Pixel and iPhone ProRAW, and Adobe DNG Converter.

PCX is the image format of ZSoft's PC Paintbrush, the standard for DOS paint programs, scanners and games before GIF and BMP took over. It compresses with a simple run-length scheme.

A PCX file has a 128-byte header (the byte 0x0A, version, encoding, bits per pixel, image window, DPI, a 16-colour palette and the number of colour planes), then RLE-compressed scanlines; 256-colour files end with the byte 0x0C and a 768-byte palette.

PCX is the better choice for DOS-era software, retro games and old fax or scanner tools, while DNG suits raw editing and archiving raw files in an open format.

PCX strengths: Read by most legacy and modern viewers; Simple, lossless run-length compression. Drawbacks to weigh: Poor compression for photographs; No transparency; Obsolete outside retro software.