Solved Make areas of existing PNG file transparent

[Daksol]

I am trying to create ICO files from existing source PNG files.
I want to make specific areas of the PNG file to be transparent.
Is there a way to "bulk fill" an area with "transparent" colour?
Thanks

[Bhikkhu Pesala]

F12 to show the paint plugin. Use the flood fill bucket to paint areas that you wish to be transparent on saving the PNG.

IrfanView only supports 24-bit PNG with a single colour for transparency. Use a proper photo-editor if you need professional results and areas that are translucent, i.e. not fully transparent.

[Daksol]

Hi thanks Bhikkhu. What I had missed before was the original PNG had not been saved with the 24bit colour depth. Once that was done the correct options were there. Thanks very much for your help.

[JendaLinda]

Bhikkhu is right.

Just for clarification, IrfanView supports following color formats:

• 2 colors - 1 bit per pixel
• 16 colors - 4 bits per pixel
• 256 colors - 8 bits per pixels
• TrueColor - 24 bits per pixels

All of them allow to pick up a single color to set it as transparent.

IrfanView does not support Alpha channel (32 bits per pixel), which would allow partial transparency.