Convert Radiance HDR to PPM / PNM

An HDR file (Radiance RGBE, .hdr or .pic) stores high dynamic range images using 32-bit floating-point-like color values, so it can record light far brighter and darker than a normal photo. It was created by Greg Ward in 1985 for the Radiance lighting simulation software and uses a simple run-length encoded format with a shared exponent per pixel.

HDR files are widely used in 3D rendering and visual effects as environment maps (HDRIs) that light a scene realistically.

Photoshop, GIMP, Affinity Photo, Blender, Krita and HDR viewers such as HDRView open .hdr files. Standard photo viewers usually can't, and screens can't show the full range, so convert HDR to JPG or PNG to get a regular image you can view and share.

The Portable Pixel Map (PPM) format is a lowest-common-denominator color image format developed by Jef Poskanzer as part of the Netpbm project. It stores pixels as uncompressed RGB triplets (Red, Green, Blue) in either a plain ASCII text format (P3 header) or a more efficient binary format (P6 header). The file structure is extremely minimal, consisting of a magic number identifier, dimensions (width and height), maximum color value, and the pixel data itself, making it easily parsable by simple scripts but inefficient for storage compared to compressed formats like JPEG or PNG.

Native support for PPM files is absent in standard Windows or macOS photo viewers. Users typically require specialized image manipulation software to view or convert these files. GIMP (GNU Image Manipulation Program) and IrfanView are the primary tools for opening PPM files on desktop environments. On Linux systems, the Netpbm toolkit and ImageMagick suite provide command-line utilities for processing and converting PPM data.