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Re: [platform-swt-dev] GTK graphics status
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Silenio_Quarti@xxxxxxx writes:
> When a image has transparency (e.g. icons, gifs with transparent pixel),
> SWT creates
> a GdkPixmap for the color part of the image and a GdkBitmap for the mask.
>
I guess the hard bit is "Image implements Drawable" - otherwise you
could just implement Image as a pixbuf instead of a pixmap.
> We are using GdkPixBuf to scale the GdkPixmap. If we use a different
> algorithm to scale the GdkBitmap, we might have problems, since different
> algorithms might replicate different pixels.
Good point.
> So if we use our own algorithm the scale a GdkBitmap, I believe we will
> have to
> use it the scale its associated GdkPixmap too.
As you probably know that's a world of pain, since you have around 20
common GdkImage pixel formats to deal with, each in two possible byte
orders...
> Right now, we are getting a GdkPixBuf with alha channel from the
> GdkPixmap,
> getting the mask data using GdkImage, combining them by replacing the
> alpha
> channel with appropriate values (e.g. 1 -> 255, 0 -> 0), scaling the
> GdkPixBuf and
> then redering to the destination drawable by calling
> gdk_pixbuf_render_to_drawable_alpha.
>
> This is somewhat inneficient though.
Yeah it's pretty ugly, but I can't think of anything much better. It
will be slow but not _that_ bad, as long as you don't do it on every
expose event or something.
There's a gdk_pixbuf_render_pixmap_and_mask() convenience function
too, FWIW, which you can use to generate a new pixmap/mask after
scaling the pixbuf.
Havoc
