BMP to EXR Converter
Convert BMP to EXR in your browser. BMP files usually come from Windows Paint, legacy Windows programs, embedded displays and some scanners; EXR is the better fit for visual effects, compositing and 3D render output. You get a ZIP-compressed OpenEXR with 16-bit half-float channels, the 8-bit sRGB values converted to linear light. Nothing is uploaded.
- Processed locally
- No upload, no wait
- No sign-up
- No watermark
Drop images here
or choose files · paste with Ctrl/⌘ V
BMP expected · other image formats also work
How to use BMP to EXR
- 1
Add your BMP files: drop them here, choose them, or paste from the clipboard.
- 2
There is nothing to tune: the EXR is written losslessly. Resizing and rotating are under More options if you need them.
- 3
Click Convert. Each file is decoded and encoded in a background thread on this device.
- 4
Download the .exr files one at a time or together as a ZIP.
Why use Aback Images for bmp to exr
Where the EXR goes next
EXR opens in Nuke, Blender, Houdini, After Effects, DaVinci Resolve, Photoshop, Krita and OpenImageIO.
EXR next to BMP
Both sides are lossless, so the size depends on how well the EXR encoder handles this picture compared with the BMP's usually none; RLE for some 4 and 8-bit files.
Written without a lossy pass
The EXR is written losslessly, so the pixels decoded from the BMP arrive unchanged.
Processed on your device
Your images are decoded, edited and encoded inside this browser tab by Web Workers. Nothing is uploaded to a server.
BMP vs EXR
What changes from BMP to EXR
Encoding: the BMP uses usually none; RLE for some 4 and 8-bit files; EXR uses none, RLE, ZIP, PIZ, PXR24, B44 or DWA, chosen per file, and the download is a ZIP-compressed OpenEXR with 16-bit half-float channels, the 8-bit sRGB values converted to linear light.
Bit depth: 1, 4, 8, 16, 24 or 32 bits per pixel in the BMP; EXR allows 16-bit half or 32-bit floating point per channel, and the EXR written here has 16-bit half float per channel.
Colour: RGB or an indexed palette in the BMP; EXR supports scene-linear RGB, often ACEScg or linear Rec.709, written here as linear-light RGB.
Transparency: the BMP stores it as an optional fourth byte in 32-bit files, which many programs ignore; the EXR keeps it as an A channel stored like any other channel.
Metadata: the BMP can carry nothing beyond the header's resolution fields (and a colour profile in rare V5 headers); EXR can carry named header attributes such as chromaticities, timecode and camera data, but nothing is copied across.
About BMP
BMP stores raw, uncompressed pixels. Files are huge but trivially simple, which is why some legacy Windows software, embedded displays and printers still ask for it.
A BMP is a 14-byte file header ('BM' and the offset to the pixels), a DIB header (40 bytes, or 108 and 124 bytes in the V4 and V5 versions that add colour masks and alpha), an optional palette, then pixel rows padded to 4 bytes and normally stored bottom-up.
BMP files usually come from Windows Paint, legacy Windows programs, embedded displays and some scanners.
About EXR
OpenEXR is the high dynamic range format of film visual effects. It stores half or full floating-point channels in linear light, plus any extra render passes, and is the working format of compositing pipelines.
An EXR starts with the magic number 76 2F 31 01 and a version field, then a header of named, typed attributes (channels, compression, dataWindow, displayWindow) and a table of offsets to scanline or tile blocks.
When converting BMP to EXR makes sense
EXR is the better choice for visual effects, compositing and 3D render output, while BMP suits legacy software and embedded systems that require it.
EXR strengths: True high dynamic range in linear light; Any number of channels and render passes; Lossless compression options. Drawbacks to weigh: Needs tone mapping to look right on a normal screen; Very large files; No browser or phone support.
Limitations
- BMP stores nearly every pixel literally, so almost any compressed target is several times smaller.
- A 32-bit BMP can carry an alpha byte that most programs ignore; if the image suddenly gains transparent areas after converting, that byte was set.
- No range is added: the EXR holds the 8-bit picture in linear light, and nothing in it is brighter than the original white.
- Compositing and 3D software read the EXR as linear light, the convention for the format, so it displays correctly there.
- The file holds colour and, when the image has transparency, an alpha channel; there are no extra render passes.
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Frequently asked questions
Does converting BMP to EXR lose quality?
EXR is written losslessly, so the pixels are stored exactly as decoded.
Is transparency kept in the EXR?
Yes. BMP stores it as an optional fourth byte in 32-bit files, which many programs ignore, and the EXR is written with an alpha channel, so transparent areas stay transparent.
Does saving as EXR add dynamic range?
No. The values come from an 8-bit image, converted to linear light so compositing software displays them correctly, but nothing brighter than the original white is invented. The file is ready to use as a plate or texture in an EXR pipeline.
Which apps open EXR files?
Nuke, Blender, Houdini, After Effects, DaVinci Resolve, Photoshop, Krita and OpenImageIO. It does not open in web browsers.
Are my images uploaded anywhere?
No. Processing happens inside your browser with WebAssembly and Web Workers. The site only downloads the app code and codecs; your files never leave your device. You can confirm this with the live upload counter on the tool, or in your browser's network panel.
Can I process many files at once?
Yes. Drop a whole selection or folder. Files are processed in parallel on several worker threads, each result can be downloaded on its own, and everything can be saved as one ZIP.
Is it free? Is there a file limit or watermark?
It is free with no account, no watermark and no daily limit. The only limit is your device's memory: very large images (over roughly 100 megapixels) may be refused to keep the tab from crashing.