PNG to HDR Converter

PNG (Portable Network Graphics) stores pixel colours as 8-bit integer values per channel in the sRGB colour space - perfect for web display but limited to the 0-255 range with gamma encoding baked in. When you convert PNG to HDR, those sRGB values are linearised and re-encoded into Radiance HDR (.hdr) - the industry-standard high-dynamic-range format developed by Greg Ward that uses RGBE (Red, Green, Blue, Exponent) encoding to represent a vastly wider luminance range. This png to hdr conversion produces a scene-linear file ready for tone-mapping, image-based lighting (IBL), and physically-based rendering (PBR) workflows.

1. 1. Upload your file: Drag and drop or browse to select your PNG or raster image file. The file is read entirely in your browser - nothing is uploaded to any server when you convert PNG to HDR online.
2. 2. sRGB linearisation & RGBE encoding: Click Convert to HDRand the tool renders your image on an HTML5 Canvas, applies the IEC 61966-2-1 sRGB inverse transfer function to convert each pixel to linear light, then encodes it as RGBE using Greg Ward's original formulation. All png to hdr processing is local and private.
3. 3. RLE compression & download: Pixel data is packed into new-style Radiance RLE scanlines and prepended with the standard Radiance header. Your png to hdr file downloads instantly - or bundled into a ZIP for batch conversions.

• Radiance ASCII header: Begins with #?RADIANCE and includes format declaration (FORMAT=32-bit_rle_rgbe), gamma, and exposure fields - readable in any text editor and required by all Radiance-compatible loaders.
• Resolution string: A single line (-Y height +X width) specifying image dimensions in the standard Radiance orientation convention used by our png to hdr converter.
• RGBE pixel data (RLE-compressed): Each scanline is stored using new-style Radiance run-length encoding with a 4-byte per-scanline header, followed by four separately compressed channels (R, G, B, E) for efficient decoding.
• 32 bits per pixel: The shared exponent (E byte) allows each RGBE pixel to represent values across roughly 76 orders of magnitude - far beyond the 0-255 range of the source PNG.

After you convert PNG to HDR, the resulting .hdr file can be opened with many professional applications. Adobe Photoshop supports HDR natively via File → Open. GIMP reads Radiance HDR with its built-in HDR plugin. darktable and Luminance HDR are free tools specialised for HDR tone-mapping. For rendering, Blender, Unreal Engine, and Unity all import .hdrfiles directly as environment maps or skybox textures. For programmatic access, Python's imageio library and OpenEXR / OpenColorIO tooling both handle RGBE HDR files, making your png to hdr output easy to integrate into any automated pipeline.