Tk Source Code

.BE
.SH DESCRIPTION
.PP
\fBTk_FindPhoto\fR returns an opaque handle that is used to identify a
particular photo image to the other procedures.  The parameter is the
name of the image, that is, the name specified to the \fBimage create
photo\fR command, or assigned by that command if no name was specified.
If \fIimageName\fR does not exist or is not a photo image, 
\fBTk_FindPhoto\fR returns NULL. 
.PP
\fBTk_PhotoPutBlock\fR is used to supply blocks of image data to be
displayed.  The call affects an area of the image of size
\fIwidth\fR x \fIheight\fR pixels, with its top-left corner at
coordinates (\fIx\fR,\fIy\fR).  All of \fIwidth\fR, \fIheight\fR,
\fIx\fR, and \fIy\fR must be non-negative.
If part of this area lies outside the

.PP
\fBTk_PhotoGetImage\fR can be used to retrieve image data from a photo
image.  \fBTk_PhotoGetImage\fR fills
in the structure pointed to by the \fIblockPtr\fR parameter with values
that describe the address and layout of the image data that the
photo image has stored internally.  The values are valid
until the image is destroyed or its size is changed.
.PP
It is possible to modify an image by writing directly to the data 
the \fIpixelPtr\fR field points to. The size of the image cannot be
changed this way, though.
Also, changes made by writing directly to \fIpixelPtr\fR will not be 
immediately visible, but only after a call to 
\fBTk_ImageChanged\fR or after an event that causes the interested 
widgets to redraw themselves.
For these reasons usually it is preferable to make changes to 
a copy of the image data and write it back with 
\fBTk_PhotoPutBlock\fR or \fBTk_PhotoPutZoomedBlock\fR. 
.PP
\fBTk_PhotoGetImage\fR returns 1 for compatibility with the
corresponding procedure in the old photo widget.
.PP
\fBTk_PhotoBlank\fR blanks the entire area of the
photo image.  Blank areas of a photo image are transparent.
.PP
\fBTk_PhotoExpand\fR requests that the widget's image be expanded to be