Re: [GD-DEVEL] save Grayscale PNG with gd

Hi Dieter,

On Nov 12, 2007 11:40 AM, Dieter Guthmann <[email protected]> wrote:
> Am I right when I guess that the same problem concerns the TIFF or
> XPM-Format?

It is nearly the same issue with PNG except when you use a palette
based image. However it will be slow as you have to first convert to
grayscale and then convert the image to a palette image.

> My original problem is that I need a high-resolution-image in a relative
> small file in PNM/PGM or XPM-File-Format (PNM is very big when it stores
> color-images)...
> When I use the pngtopnm-converter of the netpbm-package to convert from
> png to pgm/pnm then netpbm creates a (big-sized) pnm-image when the
> source is in color or it creates a (relativley small-sized) pgm-image
> when the source-file is in grayscale...

I can come with a patch later this week or during the weekend. Adding
an option to force libpng to write a grayscale image is relatively
easy. Or you may try yourself if you feel motivated enough,
contributions are always welcome :)

Best,
--Pierre