BMP to PNG

bars-32x16.bmp is a 24-bit bitmap, 32 by 16, red on the left and blue on the right. Chrome decoded it and the page wrote a 32 by 16 PNG. The grid did not change. BMP stores pixels with almost no compression, so the PNG of this icon is the smaller file you would rather keep. The conversion does not invent colour the bitmap did not have. It also does not add transparency. These bars are opaque, and the PNG is opaque. A BMP that used a palette is still decoded to pixels first. The page does not try to preserve the palette indexes. Use JPG to BMP when you are going the other way and you can accept a larger file. Use this page when an old bitmap needs a container modern tools expect.

The bitmap of the bars is the heavy file and the PNG is the one to pass on. The red half and the blue half stay on their sides. Nothing in the conversion uploads the bitmap. If a program still demands BMP, convert back only for that program and keep the PNG as the copy you edit.

Open the PNG and confirm 32 by 16 before you archive the bitmap. The left half should still read as red and the right half as blue. The conversion did not upload the file, did not add a hole, and did not try to keep palette indexes. BMP is the container you keep only when an old tool demands it. PNG is the container you edit. If the bitmap was a photograph, the PNG will be large too, just usually smaller than the uncompressed scan. These bars are the small proof of the grid, not a promise about a 20 megapixel scan.

Archive the PNG, not the bitmap, unless a named program has refused the PNG. The bars prove the grid: 32 by 16, red then blue. A 20 megapixel scan will stay large. It will usually still be smaller than its BMP. Nothing is uploaded.

Measure the PNG at 32 by 16 and then decide whether the bitmap still earns its disk space. For these bars it does not, unless an old viewer is the customer. The red half and the blue half are the visual check that the decode did not swap sides. Palette indexes are not a feature this page preserves. A scanned photograph will remain a large PNG, only usually smaller than the BMP it came from. That is the whole promise.

Put the PNG in the project and leave the bitmap next to it until you know nothing still opens the BMP. The sample is small on purpose. It shows the grid and the sides, red then blue, and it shows that a palette is not preserved. It does not show how many megabytes a scan will save. Open one real scan if that number is the decision. The page will not upload either file while you compare them. A palette inside an old bitmap is decoded to pixels and is not written back as indexes. Edit the PNG. Keep the bitmap only for a program that refuses everything else. The red half and the blue half of these bars are the visual check that the sides did not swap during that decode. Keep the PNG as the file you edit, and keep the bitmap only as the copy an old viewer still demands. A large scan stays large. These bars only prove the 32 by 16 grid and the order of the colours.

The larger uncompressed return trip is JPG to BMP.

Bitmap bars to PNG

Inputs: b2n-f: bars-32x16.bmp

On this page, take bars-32x16.bmp and press Convert. Expect the same 32 by 16 grid in a PNG.

Result: BMP to PNG: 32×16. 0.1 KB

Bitmap bars to PNG again

Inputs: b2n-f: bars-32x16.bmp

On this page, take bars-32x16.bmp and press Convert. Expect the same 32 by 16 grid in a PNG.

Result: BMP to PNG: 32×16. 0.1 KB

What size is the PNG?

32 by 16, matching the bitmap.

Is the PNG smaller?

For these bars, yes, because the bitmap was uncompressed.

Does colour change?

No new colours are invented. The decoded pixels are stored.

Is there alpha?

Not from these opaque bars.

Is the file uploaded?

No.

When do I want BMP instead?

When an old program refuses PNG. That is the other page.