GraphicsMagick: Add variants for different quantum depths

[william@…]

By adding the following lines to the portfile, the quantum depth of the graphicsmagick build may be set, allowing it to output images with a higher bit-depth than eight!

variant quantumdepth8 conflicts quantumdepth16 quantumdepth32 {
				configure.args-append --with-quantum-depth=8
}

variant quantumdepth16 conflicts quantumdepth8 quantumdepth32 {
				configure.args-append --with-quantum-depth=16
}

variant quantumdepth32 conflicts quantumdepth8 quantumdepth16 {
				configure.args-append --with-quantum-depth=32
}

[ryandesign@…]

Perhaps the variants could be named and written like they are in ImageMagick instead of inventing new names for GraphicsMagick.

In ImageMagick the default quantum depth is 16. Is it 8 in GraphicsMagick?

[william@…]

Yes, absolutely agree, revised version below.

The default quantum depth is indeed 8 in GraphicsMagick! This is mentioned in http://www.graphicsmagick.org/www/INSTALL-unix.html

Do you think we should add a "default_variants +q8" here to force this to remain a constant in the macport, or leave the default to follow GraphicsMagick's default, even if that changes in the future?

variant q8 conflicts q16 q32 description {Use 8 bits per pixel quantum (default)} {
				configure.args-append --with-quantum-depth=8
}

variant q16 conflicts q8 q32 description {Use 16 bits per pixel quantum} {
				configure.args-append --with-quantum-depth=16
}

variant q32 conflicts q8 q16 description {Use 32 bits per pixel quantum} {
				configure.args-append --with-quantum-depth=32
}

[ryandesign@…]

Thanks, I added the three variants in r39317, along with the appropriate default_variants statement to ensure that q8 is set to the default, unless the user has already selected something else. This matches what the ImageMagick port does. If GraphicsMagick ever changes its default pixel quantum depth, then the selection of the default variant should be modified accordingly.