I have +- 500 .bmp's that I would like to convert to .png's. It would be especially nice if the color white (#FFFFFF) of the original BMP's could be converted to transparent in the .png's.

PNG-8 is enough since the .bmp's are 16-colors.

I would prefer a command-line tool that I can put in a batch file, but any would be useful. Do you know of such a tool?

edit: The OS I use most is Windows 7 x64, but I also have Cygwin and various linuxes available


ImageMagick can do this - have a look at the Convert command, which allows you to specify a colour to be used as the transparency value:


  • 2
    That definitly seems promising. conver -transparent white source.bmp dest.png does exactly what I want, however only mogrify supports multiple files and it only has -transparent-color which doesn't really work. Looking further – dtech Sep 26 '11 at 19:35
  • Ultimately I just used a script with a loop. For those, interested, effictive code was convert -transparent white $f ${f%bmp}png – dtech Sep 26 '11 at 20:26
  • @dtech: and your system was Windows, Linux, Mac, android.... ? – woliveirajr Sep 26 '11 at 20:27
  • @woliveirajr it was a bash shell, other shells should allow simalar constructs – dtech Sep 29 '11 at 12:24
  • if you want to run it as a bash script for batch conversion in a whole folder full of files: for file in *.png ; do convert "${file}" -transparent '#ffcc66' "batch/${file}" ; done – Sameer Shemna Oct 21 '14 at 10:09

Using what operating system, etc ?

One suggestion - generic answer: give a try to ImageMagik.

Right from the first page you can get:

Format conversion: convert an image from one format to another (e.g. PNG to JPEG). Transparency: render portions of an image invisible.

Usage example:

convert file.jpg -transparent-color '#ffffff' file.png

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.