JPG to BMP

bars-32x16.jpg becomes a 24-bit BMP that is 32 pixels wide and 16 tall. The header starts with BM. The rows are bottom-up, which is the ordinary bitmap layout. The file is larger than the JPEG because BMP does not compress these pixels. Nothing the JPEG threw away comes back. The page is honest about that. There is no alpha channel in this BMP. A transparent logo cannot travel through a JPEG and reappear here. Use this when a very old program refuses every container except BMP. Use PNG when you want a smaller lossless file instead.

BM at the front and 32 by 16 in the header are the checks. The JPEG bytes are not stored inside the BMP. They are decoded and written as plain pixels, which is why the file grows and why blur stays blur. Keep the JPEG if the BMP was a test.

The BM header and the 32 by 16 size are the whole success condition. The file is larger because the pixels are written out plain. The JPEG compression that made the source small is gone, and the detail that compression removed is still gone. Use the BMP for the old program, then go back to the JPEG or to a PNG for everything else. There is no alpha channel to negotiate. A logo that needed a hole cannot get that hole back by this route.

Hand the BMP to the old program and keep the JPEG. The header is BM and the size is 32 by 16. The file grew because the pixels are plain. Sharpness did not return. A hole did not return. Those two limits are the page.

Give the old program the BMP and keep the JPEG for yourself. BM and 32 by 16 are the checks that the unpack worked. The file is larger on purpose. Blur stays. A hole does not reappear. If the old program can be taught to open PNG, prefer that smaller lossless file and skip this page. The JPEG is not uploaded while you decide. BM and 32 by 16 mean the unpack worked, and a larger file is the expected cost of plain pixels.

The old program gets the BMP. You keep the JPEG. If the old program can open PNG, use that page instead and skip the larger file. BM at the start and 32 by 16 in the header are how you know this unpack worked. Blur stays blur. A hole stays missing. Those are the limits, and they are the reason this page is a compatibility exit rather than a place to edit. Keep the JPEG beside the BMP until the old program has actually opened the bitmap. Plain pixels are larger, and that growth is the point of the unpack, not a sign that the JPEG was damaged on the way out. Plain rows are bigger. That is the unpack, and it is why the BMP is not the file you keep editing afterwards. Return to the JPEG for any further work.

A smaller lossless file is JPG to PNG.

JPEG bars unpacked

Inputs: j2b-f: bars-32x16.jpg

On this page, take bars-32x16.jpg and press Convert to BMP. Expect a larger BM file, not a sharper picture.

Result: JPG to BMP: 32×16. 1.6 KB

JPEG bars unpacked again

Inputs: j2b-f: bars-32x16.jpg

On this page, take bars-32x16.jpg and press Convert to BMP. Expect a larger BM file, not a sharper picture.

Result: JPG to BMP: 32×16. 1.6 KB

How wide is the bitmap?

32 pixels, and it is 16 tall.

Why is the file bigger?

These pixels are stored without JPEG compression.

Does sharpness come back?

No.

Can the BMP be transparent?

Not this 24-bit file.

Is the JPEG uploaded?

No.

What if I wanted PNG?

Use JPG to PNG. It is smaller and still lossless relative to the decoded pixels.