1Tk_GetImage(3) Tk Library Procedures Tk_GetImage(3)
2______________________________________________________________________________
6
8 Tk_GetImage, Tk_RedrawImage, Tk_SizeOfImage, Tk_FreeImage - use an
9 image in a widget
10
12 #include <tk.h>
13 Tk_Image
15 Tk_GetImage(interp, tkwin, name, changeProc, clientData)
16 Tk_RedrawImage(image, imageX, imageY, width, height, drawable, drawableX, drawableY)
18 Tk_SizeOfImage(image, widthPtr, heightPtr)
20 Tk_FreeImage(image)
22
24 Tcl_Interp *interp (in) Place to leave error mes‐
25 sage.
26 Tk_Window tkwin (in) Window in which image
28 will be used.
29 const char *name (in) Name of image.
31 Tk_ImageChangedProc *changeProc (in) Procedure for Tk to
33 invoke whenever image
34 content or size changes.
35 ClientData clientData (in) One-word value for Tk to
37 pass to changeProc.
38 Tk_Image image (in) Token for image instance;
40 must have been returned
41 by a previous call to
42 Tk_GetImage.
43 int imageX (in) X-coordinate of upper-
45 left corner of region of
46 image to redisplay (mea‐
47 sured in pixels from the
48 image's upper-left cor‐
49 ner).
50 int imageY (in) Y-coordinate of upper-
52 left corner of region of
53 image to redisplay (mea‐
54 sured in pixels from the
55 image's upper-left cor‐
56 ner).
57 int width ((in)) Width of region of image
59 to redisplay.
60 int height ((in)) Height of region of image
62 to redisplay.
63 Drawable drawable (in) Where to display image.
65 Must either be window
66 specified to Tk_GetImage
67 or a pixmap compatible
68 with that window.
69 int drawableX (in) Where to display image in
71 drawable: this is the x-
72 coordinate in drawable
73 where x-coordinate imageX
74 of the image should be
75 displayed.
76 int drawableY (in) Where to display image in
78 drawable: this is the y-
79 coordinate in drawable
80 where y-coordinate imageY
81 of the image should be
82 displayed.
83 int widthPtr (out) Store width of image (in
85 pixels) here.
86 int heightPtr (out) Store height of image (in
88 pixels) here.
89_________________________________________________________________
90
93 These procedures are invoked by widgets that wish to display images.
94 Tk_GetImage is invoked by a widget when it first decides to display an
95 image. name gives the name of the desired image and tkwin identifies
96 the window where the image will be displayed. Tk_GetImage looks up the
97 image in the table of existing images and returns a token for a new
98 instance of the image. If the image does not exist then Tk_GetImage
99 returns NULL and leaves an error message in interp->result.
100 When a widget wishes to actually display an image it must call
102 Tk_RedrawImage, identifying the image (image), a region within the
103 image to redisplay (imageX, imageY, width, and height), and a place to
104 display the image (drawable, drawableX, and drawableY). Tk will then
105 invoke the appropriate image manager, which will display the requested
106 portion of the image before returning.
107 A widget can find out the dimensions of an image by calling Tk_Size‐
109 OfImage: the width and height will be stored in the locations given by
110 widthPtr and heightPtr, respectively.
111 When a widget is finished with an image (e.g., the widget is being
113 deleted or it is going to use a different image instead of the current
114 one), it must call Tk_FreeImage to release the image instance. The
115 widget should never again use the image token after passing it to
116 Tk_FreeImage. There must be exactly one call to Tk_FreeImage for each
117 call to Tk_GetImage.
118 If the contents or size of an image changes, then any widgets using the
120 image will need to find out about the changes so that they can redis‐
121 play themselves. The changeProc and clientData arguments to Tk_GetIm‐
122 age are used for this purpose. changeProc will be called by Tk when‐
123 ever a change occurs in the image; it must match the following proto‐
124 type:
125 typedef void Tk_ImageChangedProc(
126 ClientData clientData,
127 int x,
128 int y,
129 int width,
130 int height,
131 int imageWidth,
132 int imageHeight);
133 The clientData argument to changeProc is the same as the clientData
134 argument to Tk_GetImage. It is usually a pointer to the widget record
135 for the widget or some other data structure managed by the widget. The
136 arguments x, y, width, and height identify a region within the image
137 that must be redisplayed; they are specified in pixels measured from
138 the upper-left corner of the image. The arguments imageWidth and
139 imageHeight give the image's (new) size.
140
143 Tk_CreateImageType
144
147 images, redisplay
148Tk 4.0 Tk_GetImage(3)