Convert BMP to transparent PNG

[Markus Breitinger]

I have a collection of Windows BMP files which use the color of upper left corner to define the transparent background. The target should be PNG files.

I tried:
convert MOT01_MOT_AP_GROSS_AUS.bmp -transparent %[pixel:p{0,0}] MOT01_MOT_AP_GROSS_AUS.png

but somehow it is wrong. Could you please help me!

[snibgo]

Sadly, "-transparent" needs an actual colour, and can't accept a "pixel:" expression.

I don't think this can be done in a single convert. We can do it in two converts. The first gets the colour. For example, Windows BAT format:

Code: Select all

for /F "usebackq" %%C ^
in (`%IM%convert x.bmp -format "%%[pixel:p{0,0}]" info:`) ^
do set ONE_PIXEL=%%C

%IM%convert x.bmp -transparent %ONE_PIXEL% x.png

[fmw42]

there is a way to do the equivalent in one command. you can even add -fuzz XX% if you want

Code: Select all

convert image.bmp -fill none -draw "matte 0,0 replace" newimage.png

[snibgo]

Ah, brilliant, thanks. I thought I might be forgetting something.

[Markus Breitinger]

Thank you very much! Works great.