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| author | Havoc Pennington <hp@pobox.com> | 1999-11-04 20:16:17 +0000 |
|---|---|---|
| committer | Havoc Pennington <hp@src.gnome.org> | 1999-11-04 20:16:17 +0000 |
| commit | 085a27d3305a68969728eb6cab4fb95973ef8fa9 (patch) | |
| tree | d22e6bfca56cf05e12954d8f93c0c6f9a48f44a1 /gdk/gdkpixbuf-render.c | |
| parent | 38abc0dee0672b1fa07ca2b27cfad1112cfffa3e (diff) | |
| download | gdk-pixbuf-085a27d3305a68969728eb6cab4fb95973ef8fa9.tar.gz | |
In docs, explain what a dither offset is for.
1999-11-04 Havoc Pennington <hp@pobox.com>
* src/gdk-pixbuf-render.c (gdk_pixbuf_render_to_drawable): In
docs, explain what a dither offset is for.
(gdk_pixbuf_render_to_drawable_alpha): Explain why you would use
this function vs. gdk_pixbuf_render_to_drawable().
Diffstat (limited to 'gdk/gdkpixbuf-render.c')
| -rw-r--r-- | gdk/gdkpixbuf-render.c | 13 |
1 files changed, 13 insertions, 0 deletions
diff --git a/gdk/gdkpixbuf-render.c b/gdk/gdkpixbuf-render.c index a12e8ae66..147403c36 100644 --- a/gdk/gdkpixbuf-render.c +++ b/gdk/gdkpixbuf-render.c @@ -43,6 +43,7 @@ * Takes the opacity values in a rectangular portion of a pixbuf and thresholds * them to produce a bi-level alpha mask that can be used as a clipping mask for * a drawable. + * **/ void gdk_pixbuf_render_threshold_alpha (GdkPixbuf *pixbuf, GdkBitmap *bitmap, @@ -174,6 +175,11 @@ remove_alpha (ArtPixBuf *apb, int x, int y, int width, int height, int *rowstrid * the GdkRGB visual and colormap. Note that this function will ignore the * opacity information for images with an alpha channel; the GC must already * have the clipping mask set if you want transparent regions to show through. + * + * For an explanation of dither offsets, see the GdkRGB documentation. In brief, the + * dither offset is important when scrolling (so you can redraw half an image but keep the + * dithering "lined up" between the part you drew first and the part you drew previously). + * For unscrolled images, the offset can always be 0. **/ void gdk_pixbuf_render_to_drawable (GdkPixbuf *pixbuf, @@ -247,6 +253,13 @@ gdk_pixbuf_render_to_drawable (GdkPixbuf *pixbuf, * * Renders a rectangular portion of a pixbuf to a drawable. This is done using * GdkRGB, so the specified drawable must have the GdkRGB visual and colormap. + * + * This function has a performance penalty; it makes two synchronous + * round trips to the X server (creating a bitmask and a GC), and it + * draws the contents of the bitmask. If performance is crucial, + * consider handling alpha yourself and using + * gdk_pixbuf_render_to_drawable(). On the other hand it's more convenient + * than gdk_pixbuf_render_to_drawable() because it handles the alpha channel. **/ void gdk_pixbuf_render_to_drawable_alpha (GdkPixbuf *pixbuf, GdkDrawable *drawable, |