From 085a27d3305a68969728eb6cab4fb95973ef8fa9 Mon Sep 17 00:00:00 2001 From: Havoc Pennington Date: Thu, 4 Nov 1999 20:16:17 +0000 Subject: [PATCH] In docs, explain what a dither offset is for. 1999-11-04 Havoc Pennington * 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(). --- gdk-pixbuf/ChangeLog | 7 +++++++ gdk/gdkpixbuf-render.c | 13 +++++++++++++ 2 files changed, 20 insertions(+) diff --git a/gdk-pixbuf/ChangeLog b/gdk-pixbuf/ChangeLog index 8df225dee6..b53e541404 100644 --- a/gdk-pixbuf/ChangeLog +++ b/gdk-pixbuf/ChangeLog @@ -1,3 +1,10 @@ +1999-11-04 Havoc Pennington + + * 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(). + 1999-11-04 Havoc Pennington * configure.in: Use libart-config correctly; find gnome-config diff --git a/gdk/gdkpixbuf-render.c b/gdk/gdkpixbuf-render.c index a12e8ae66a..147403c365 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, -- 2.30.2