How to use
- Open bars-32x16.png.
- Expect a 32 by 16 BMP.
- Expect white only if a pixel had been transparent.
Formula / how it works
bars-32x16.png becomes the same kind of 24-bit BMP, 32 by 16, header BM. A transparent pixel would be painted white first, because this BMP cannot store a hole. These bars are opaque, so the white rule is a warning for a logo, not a change in the sample. The file grows, because the PNG was compressed and the BMP is not. The grid does not change. Keep the PNG if you do not specifically need BMP. The download does not replace the PNG on disk.
Opaque bars do not show the white-box problem. A logo with a transparent edge will. Paint happens before the 24-bit rows are written. The PNG is still the file with the hole, if there was a hole. These bars had none. The BMP is the compatibility copy.
Twenty-four bits means the hole, if there was one, became white before the rows were stored. The bars had no hole, so the sample looks like a straight copy at 32 by 16. A logo with soft transparent edges will grow a white fringe. That is the limit to read before you convert the logo. The PNG with the hole is still on disk. The BMP is the compatibility file, and it is the heavier one. Keep both until the old program has opened the BMP.
Logos with a soft edge pick up white. These bars do not, and that is why they are the wrong file for testing the fringe. Test a logo before you convert a set of them. The PNG with the hole remains. The BMP is heavier and opaque.
Try a logo with a soft edge before you batch a folder, because these bars will not show the white fringe. The fringe is white because the BMP is 24-bit. The bars are 32 by 16 and opaque, so they look like a copy. The PNG is the file that still has a hole, when there was a hole. Keep it. The BMP is the heavy compatibility copy and nothing more.
Convert one logo with a soft edge and look for the white fringe before you convert a hundred. The bars will not warn you, because they are opaque and 32 by 16. The fringe is the 24-bit limit. The PNG still has the hole. The BMP does not, and it is heavier. Keep the PNG as the master. Treat the BMP as the file you hand to the program that asked for it. The bars will not show a white fringe. A soft-edged logo will. Convert that logo once before a folder of them. The bars are the opaque control sample, 32 by 16, and they will not reveal the fringe a soft logo will. Convert one soft-edged logo, look at the white edge, and only then decide whether BMP is acceptable for that logo. The bars sample cannot make the decision for you. Look at one soft-edged logo, then decide if the white fringe is acceptable on that logo and on every other file in the set. The bars cannot show you that white fringe.
Keep transparency by staying on PNG to JPG only if white is acceptable, or keep the PNG.
Worked examples
PNG bars as BMP
Inputs: n2b-f: bars-32x16.png
On this page, take bars-32x16.png and press Convert to BMP. A transparent pixel would be painted white.
Result: PNG to BMP: 32×16. 1.6 KB
PNG bars as BMP again
Inputs: n2b-f: bars-32x16.png
On this page, take bars-32x16.png and press Convert to BMP. A transparent pixel would be painted white.
Result: PNG to BMP: 32×16. 1.6 KB
Use cases
- Handing BMP to an old tool.
- Accepting a larger file.
- Painting holes white.
- Keeping the grid.
Tips & limitations
- These bars are opaque.
- A logo with a hole will gain a white box.
- The PNG stays on disk.
- 24-bit means no alpha in the BMP.
FAQ
What size is the BMP?
32 by 16.
Why would it grow?
The PNG was compressed. The BMP is not.
Where does transparency go?
Onto white.
Is the header BM?
Yes.
Is the PNG uploaded?
No.
Should I delete the PNG?
Only after the old program has opened the BMP.
White corners are a risk for a transparent logo, not for these opaque bars.