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Functions
GdkPixbuf * | gdk_pixbuf_scale_simple () |
void | gdk_pixbuf_scale () |
GdkPixbuf * | gdk_pixbuf_composite_color_simple () |
void | gdk_pixbuf_composite () |
void | gdk_pixbuf_composite_color () |
GdkPixbuf * | gdk_pixbuf_rotate_simple () |
GdkPixbuf * | gdk_pixbuf_flip () |
Description
The GdkPixBuf contains functions to scale pixbufs, to scale pixbufs and alpha blend against an existing image, and to scale pixbufs and alpha blend against a solid color or checkerboard. Alpha blending a checkerboard is a common way to show an image with an alpha channel in image-viewing and editing software.
Note that in these functions, the terms ‘alpha blending’ and ‘compositing’ are used synonymously.
Since the full-featured functions (gdk_pixbuf_scale()
,
gdk_pixbuf_composite()
, and gdk_pixbuf_composite_color()
) are
rather complex to use and have many arguments, two simple
convenience functions are provided, gdk_pixbuf_scale_simple()
and
gdk_pixbuf_composite_color_simple()
which create a new pixbuf of a
given size, scale an original image to fit, and then return the
new pixbuf.
If the destination pixbuf was created from a readonly source, these operations will force a copy into a mutable buffer.
Scaling and alpha blending functions take advantage of MMX hardware
acceleration on systems where MMX is supported. If gdk-pixbuf is built
with the Sun mediaLib library, these functions are instead accelerated
using mediaLib, which provides hardware acceleration on Intel, AMD,
and Sparc chipsets. If desired, mediaLib support can be turned off by
setting the GDK_DISABLE_MEDIALIB
environment variable.
The alpha blending function used is:
Cd = Cs·As + Cd(1-As)
where Cd
is the destination pixel color, Cs
is the source pixel color,
and As
is the source pixel alpha.
Functions
gdk_pixbuf_scale_simple ()
GdkPixbuf * gdk_pixbuf_scale_simple (const GdkPixbuf *src
,int dest_width
,int dest_height
,GdkInterpType interp_type
);
Create a new GdkPixbuf containing a copy of src
scaled to
dest_width
x dest_height
. Leaves src
unaffected. interp_type
should be GDK_INTERP_NEAREST if you want maximum speed (but when
scaling down GDK_INTERP_NEAREST is usually unusably ugly). The
default interp_type
should be GDK_INTERP_BILINEAR which offers
reasonable quality and speed.
You can scale a sub-portion of src
by creating a sub-pixbuf
pointing into src
; see gdk_pixbuf_new_subpixbuf()
.
If dest_width
and dest_height
are equal to the src
width and height, a
copy of src
is returned, avoiding any scaling.
For more complicated scaling/alpha blending see gdk_pixbuf_scale()
and gdk_pixbuf_composite()
.
Parameters
src |
||
dest_width |
the width of destination image |
|
dest_height |
the height of destination image |
|
interp_type |
the interpolation type for the transformation. |
Returns
the new GdkPixbuf, or NULL
if not enough memory could be
allocated for it.
[nullable][transfer full]
gdk_pixbuf_scale ()
void gdk_pixbuf_scale (const GdkPixbuf *src
,GdkPixbuf *dest
,int dest_x
,int dest_y
,int dest_width
,int dest_height
,double offset_x
,double offset_y
,double scale_x
,double scale_y
,GdkInterpType interp_type
);
Creates a transformation of the source image src
by scaling by
scale_x
and scale_y
then translating by offset_x
and offset_y
,
then renders the rectangle (dest_x
, dest_y
, dest_width
,
dest_height
) of the resulting image onto the destination image
replacing the previous contents.
Try to use gdk_pixbuf_scale_simple()
first, this function is
the industrial-strength power tool you can fall back to if
gdk_pixbuf_scale_simple()
isn't powerful enough.
If the source rectangle overlaps the destination rectangle on the same pixbuf, it will be overwritten during the scaling which results in rendering artifacts.
Parameters
src |
||
dest |
the GdkPixbuf into which to render the results |
|
dest_x |
the left coordinate for region to render |
|
dest_y |
the top coordinate for region to render |
|
dest_width |
the width of the region to render |
|
dest_height |
the height of the region to render |
|
offset_x |
the offset in the X direction (currently rounded to an integer) |
|
offset_y |
the offset in the Y direction (currently rounded to an integer) |
|
scale_x |
the scale factor in the X direction |
|
scale_y |
the scale factor in the Y direction |
|
interp_type |
the interpolation type for the transformation. |
gdk_pixbuf_composite_color_simple ()
GdkPixbuf * gdk_pixbuf_composite_color_simple (const GdkPixbuf *src
,int dest_width
,int dest_height
,GdkInterpType interp_type
,int overall_alpha
,int check_size
,guint32 color1
,guint32 color2
);
Creates a new GdkPixbuf by scaling src
to dest_width
x
dest_height
and alpha blending the result with a checkboard of colors
color1
and color2
.
Parameters
src |
||
dest_width |
the width of destination image |
|
dest_height |
the height of destination image |
|
interp_type |
the interpolation type for the transformation. |
|
overall_alpha |
overall alpha for source image (0..255) |
|
check_size |
the size of checks in the checkboard (must be a power of two) |
|
color1 |
the color of check at upper left |
|
color2 |
the color of the other check |
Returns
the new GdkPixbuf, or NULL
if not enough memory could be
allocated for it.
[nullable][transfer full]
gdk_pixbuf_composite ()
void gdk_pixbuf_composite (const GdkPixbuf *src
,GdkPixbuf *dest
,int dest_x
,int dest_y
,int dest_width
,int dest_height
,double offset_x
,double offset_y
,double scale_x
,double scale_y
,GdkInterpType interp_type
,int overall_alpha
);
Creates a transformation of the source image src
by scaling by
scale_x
and scale_y
then translating by offset_x
and offset_y
.
This gives an image in the coordinates of the destination pixbuf.
The rectangle (dest_x
, dest_y
, dest_width
, dest_height
)
is then alpha blended onto the corresponding rectangle of the
original destination image.
When the destination rectangle contains parts not in the source image, the data at the edges of the source image is replicated to infinity.
Parameters
src |
||
dest |
the GdkPixbuf into which to render the results |
|
dest_x |
the left coordinate for region to render |
|
dest_y |
the top coordinate for region to render |
|
dest_width |
the width of the region to render |
|
dest_height |
the height of the region to render |
|
offset_x |
the offset in the X direction (currently rounded to an integer) |
|
offset_y |
the offset in the Y direction (currently rounded to an integer) |
|
scale_x |
the scale factor in the X direction |
|
scale_y |
the scale factor in the Y direction |
|
interp_type |
the interpolation type for the transformation. |
|
overall_alpha |
overall alpha for source image (0..255) |
gdk_pixbuf_composite_color ()
void gdk_pixbuf_composite_color (const GdkPixbuf *src
,GdkPixbuf *dest
,int dest_x
,int dest_y
,int dest_width
,int dest_height
,double offset_x
,double offset_y
,double scale_x
,double scale_y
,GdkInterpType interp_type
,int overall_alpha
,int check_x
,int check_y
,int check_size
,guint32 color1
,guint32 color2
);
Creates a transformation of the source image src
by scaling by
scale_x
and scale_y
then translating by offset_x
and offset_y
,
then alpha blends the rectangle (dest_x
,dest_y
, dest_width
,
dest_height
) of the resulting image with a checkboard of the
colors color1
and color2
and renders it onto the destination
image.
If the source image has no alpha channel, and overall_alpha
is 255, a fast
path is used which omits the alpha blending and just performs the scaling.
See gdk_pixbuf_composite_color_simple()
for a simpler variant of this
function suitable for many tasks.
Parameters
src |
||
dest |
the GdkPixbuf into which to render the results |
|
dest_x |
the left coordinate for region to render |
|
dest_y |
the top coordinate for region to render |
|
dest_width |
the width of the region to render |
|
dest_height |
the height of the region to render |
|
offset_x |
the offset in the X direction (currently rounded to an integer) |
|
offset_y |
the offset in the Y direction (currently rounded to an integer) |
|
scale_x |
the scale factor in the X direction |
|
scale_y |
the scale factor in the Y direction |
|
interp_type |
the interpolation type for the transformation. |
|
overall_alpha |
overall alpha for source image (0..255) |
|
check_x |
the X offset for the checkboard (origin of checkboard is at - |
|
check_y |
the Y offset for the checkboard |
|
check_size |
the size of checks in the checkboard (must be a power of two) |
|
color1 |
the color of check at upper left |
|
color2 |
the color of the other check |
gdk_pixbuf_rotate_simple ()
GdkPixbuf * gdk_pixbuf_rotate_simple (const GdkPixbuf *src
,GdkPixbufRotation angle
);
Rotates a pixbuf by a multiple of 90 degrees, and returns the result in a new pixbuf.
If angle
is 0, a copy of src
is returned, avoiding any rotation.
Returns
the new GdkPixbuf, or NULL
if not enough memory could be allocated for it.
[nullable][transfer full]
Since: 2.6
Types and Values
enum GdkInterpType
This enumeration describes the different interpolation modes that
can be used with the scaling functions. GDK_INTERP_NEAREST
is
the fastest scaling method, but has horrible quality when
scaling down. GDK_INTERP_BILINEAR
is the best choice if you
aren't sure what to choose, it has a good speed/quality balance.
**Note**: Cubic filtering is missing from the list; hyperbolic interpolation is just as fast and results in higher quality.
Members
Nearest neighbor sampling; this is the fastest and lowest quality mode. Quality is normally unacceptable when scaling down, but may be OK when scaling up. |
||
This is an accurate simulation of the PostScript image operator without any interpolation enabled. Each pixel is rendered as a tiny parallelogram of solid color, the edges of which are implemented with antialiasing. It resembles nearest neighbor for enlargement, and bilinear for reduction. |
||
Best quality/speed balance; use this mode by default. Bilinear interpolation. For enlargement, it is equivalent to point-sampling the ideal bilinear-interpolated image. For reduction, it is equivalent to laying down small tiles and integrating over the coverage area. |
||
This is the slowest and highest quality
reconstruction function. It is derived from the hyperbolic filters in
Wolberg's "Digital Image Warping", and is formally defined as the
hyperbolic-filter sampling the ideal hyperbolic-filter interpolated
image (the filter is designed to be idempotent for 1:1 pixel mapping).
**Deprecated**: this interpolation filter is deprecated, as in reality
it has a lower quality than the |
enum GdkPixbufRotation
The possible rotations which can be passed to gdk_pixbuf_rotate_simple()
.
To make them easier to use, their numerical values are the actual degrees.