merging imread and imwrite

[John W. Eaton]

On  1-Feb-2008, Daniel J Sebald wrote:

| Looking at "imread" I notice that JPEG and PNG files are actually
| handled separate from ImageMagick, via pngread() and jpgread().  So
| if there is a bug, it is in pngread().

By using Magick++ to read all image files, I would hope to eliminate
most problems like this.

| I see that pngread() is a C++ file.  I typed "type pngread" and
| Octave spits out all the ASCII characters in computer hieroglyphics.
| Is it supposed to do that for .cc functions? 

No, that's a bug.  Thanks for reminding me about it.

| Anyway, as it currently stands, it appears that ImageMagick isn't
| all that would be needed for the port you are discussing.  Two of
| the significant formats are handled differently.  Does that have any
| significance to the discussion?

They don't have to be handled differently.  We can use Magick++ to
read png and jpeg files, though I think it ultimately uses libpng and
libjpeg to actually read them.

I think the original intent of the imread code was to work for jpeg or
png files even if Magick++ libraries were not installed, but the logic
there seems a bit backward.  I think I would have had it try Magick++
first.

In any case, I think I'd like to just use Magick++ to read and write
image files when we move this code from the Octave Forge image package
to Octave.

jwe