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Diffstat (limited to 'gdk-pixbuf/gdk-pixbuf.c')
-rw-r--r-- | gdk-pixbuf/gdk-pixbuf.c | 68 |
1 files changed, 68 insertions, 0 deletions
diff --git a/gdk-pixbuf/gdk-pixbuf.c b/gdk-pixbuf/gdk-pixbuf.c index f38ad8aa3..2594b99e9 100644 --- a/gdk-pixbuf/gdk-pixbuf.c +++ b/gdk-pixbuf/gdk-pixbuf.c @@ -99,6 +99,74 @@ * an older variant that predates the existence of #GBytes. */ +/** + * SECTION:gdk-pixbuf + * @Short_description: Information that describes an image. + * @Title: The GdkPixbuf Structure + * + * The #GdkPixbuf structure contains + * information that describes an image in memory. + * + * ## Image Data ## {#image-data} + * + * Image data in a pixbuf is stored in memory in uncompressed, + * packed format. Rows in the image are stored top to bottom, and + * in each row pixels are stored from left to right. There may be + * padding at the end of a row. The "rowstride" value of a pixbuf, + * as returned by gdk_pixbuf_get_rowstride(), indicates the number + * of bytes between rows. + * + * ## put_pixel() Example ## {#put-pixel} + * + * The following code illustrates a simple put_pixel() + * function for RGB pixbufs with 8 bits per channel with an alpha + * channel. It is not included in the gdk-pixbuf library for + * performance reasons; rather than making several function calls + * for each pixel, your own code can take shortcuts. + * + * |[<!-- language="C" --> + * static void + * put_pixel (GdkPixbuf *pixbuf, int x, int y, guchar red, guchar green, guchar blue, guchar alpha) + * { + * int width, height, rowstride, n_channels; + * guchar *pixels, *p; + * + * n_channels = gdk_pixbuf_get_n_channels (pixbuf); + * + * g_assert (gdk_pixbuf_get_colorspace (pixbuf) == GDK_COLORSPACE_RGB); + * g_assert (gdk_pixbuf_get_bits_per_sample (pixbuf) == 8); + * g_assert (gdk_pixbuf_get_has_alpha (pixbuf)); + * g_assert (n_channels == 4); + * + * width = gdk_pixbuf_get_width (pixbuf); + * height = gdk_pixbuf_get_height (pixbuf); + * + * g_assert (x >= 0 && x < width); + * g_assert (y >= 0 && y < height); + * + * rowstride = gdk_pixbuf_get_rowstride (pixbuf); + * pixels = gdk_pixbuf_get_pixels (pixbuf); + * + * p = pixels + y * rowstride + x * n_channels; + * p[0] = red; + * p[1] = green; + * p[2] = blue; + * p[3] = alpha; + * } + * ]| + * + * This function will not work for pixbufs with images that are + * other than 8 bits per sample or channel, but it will work for + * most of the pixbufs that GTK+ uses. + * + * If you are doing memcpy() of raw pixbuf data, note that the last row + * in the pixbuf may not be as wide as the full rowstride, but rather + * just as wide as the pixel data needs to be. That is, it is unsafe to + * do `memcpy (dest, pixels, rowstride * height)` to copy a whole pixbuf. + * Use gdk_pixbuf_copy() instead, or compute the width in bytes of the + * last row as `width * ((n_channels * bits_per_sample + 7) / 8)`. + */ + static void gdk_pixbuf_finalize (GObject *object); static void gdk_pixbuf_set_property (GObject *object, guint prop_id, |