Question 1

Which BMP variants are supported?

Accepted Answer

All the common ones: uncompressed (BI_RGB) 1/4/8/16/24/32-bit, RLE8 and RLE4 compressed files, BI_BITFIELDS colour masks with alpha, and both bottom-up and top-down row order. The rare BMPs with an embedded JPEG or PNG inside (BI_JPEG/BI_PNG) are honestly refused.

Question 2

Why is my 32-bit BMP's fourth channel ignored?

Accepted Answer

Plain 32-bit BI_RGB files keep that byte reserved — browsers and image editors treat it the same way. When the file actually declares an alpha mask (BI_BITFIELDS/ALPHABITFIELDS or V4/V5 headers), transparency is honoured and the page embeds lossless PNG.

Question 3

BMP files are huge — is there a limit?

Accepted Answer

Each image may be up to 40 megapixels (about 160 MB of pixel data) — anything larger is refused honestly, because decoding it could exhaust the browser's memory. Convert oversized files in smaller crops, or run Compress PDF on the result.

BMP to PDF

How it works

Frequently asked

How it works

Frequently asked

Which BMP variants are supported?

Why is my 32-bit BMP's fourth channel ignored?

BMP files are huge — is there a limit?

Search tools