Have just upgraded from old Pronto to PPNG.

I have some old images that I'd like to reuse in my new PPNG pcf. Unfortunately, they were anti-aliased with a fixed matte colour (ah, bmp). I would like to extract them as real transparent PNGs. Fortunately, the matte colour is white, so this looks easy in theory.

My approach so far has been to experiment with using filters to provide some sort of mask, but I'm now way beyond my regular Photoshop experience. I have also tried using the background eraser (which says it performs colour extraction). However, I still have an image with grey pixels rather than black pixels in a variety of transparencies.

I'm currently using Photoshop Elements, but I have a copy of the full product (pre-CS, v7?) - just never felt the need to install. Is this the time? Reluctant to install just to see whether it has better alpha channel support.

Would appreciate any advice on best tools for this sort of task and a mini-walkthrough. I've had a reasonable amount of experience in creating transparent PNGs from scratch, so I should be able to follow an explanation. But I don't really want to have to create these images again from scratch as I have no discernible artistic talent, which makes the process long and tedious!

A search of the forum provides a number of references to PSP8 and "the PNG optimiser". Is that a feature of PSP? Don't really want to have to have PSP and Photoshop! Just off to explore gimp and Xara, but would rather stick with the program I know.

Not sure what you are tryin to do.

What do you mean by "real transparent PNGs"?

Are you trying to out a white background without having jaggy edges?

What do you mean by "black pixels in a variety of transparencies"?

I think you have understood, in spite of your questions!

I have a greyscale image on a white background (the matte). It has anti-aliased edges (to avoid jaggies). However, I would like to "lift" the image and leave the background behind. This should leave me with what is effectively a black image. The edge pixels that were grey would now be black, but in a varying degree of transparency (since this is what the grey anti-aliasing on a white matte simulates).

I'm far from a Photoshop guru, but it sounds like it would be faster to start from scratch. The only way I can think to achieve what you want is to create mutiple layers, one for each color, and adjust the transparency of each independently. What kind of graphics are you doing? Something that is readily available as a png in the files area here, perhaps?

Check out this site:



Sounds close enough to what you're looking for.

I read you message about 3 times. If I understood I would not have asked!

Anyway, try this.

Resize image to 1000 percent.

Adjust levels to improve contrast.

Make a duplicate of your background layer and delete background layer as it is not needed anymore.

Set magic wand tolerance to something like 10 to start (you may need to experiment with differend values) and check Anti-aliased.

Select all white areas (hold shift to add to your selection).

Expand selection 1 pixel (Menu: Select/Modify/Expand) and press delete. Check results and repeat as needed.

Reduce size back to original (10 percent of current size), and save as PNG (do not flatten).

This message was edited by Rasterblaster on 04/20/04 05:37.

Thanks both for your suggestions, I'll try them out as soon as I get a chance.