1Tk_GetImage(3) Tk Library Procedures Tk_GetImage(3)
2______________________________________________________________________________
6
8 Tk_GetImage, Tk_RedrawImage, Tk_SizeOfImage, Tk_FreeImage - use an im‐
9 age 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 in‐
33 voke whenever image con‐
34 tent 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
92 These procedures are invoked by widgets that wish to display images.
93 Tk_GetImage is invoked by a widget when it first decides to display an
94 image. name gives the name of the desired image and tkwin identifies
95 the window where the image will be displayed. Tk_GetImage looks up the
96 image in the table of existing images and returns a token for a new in‐
97 stance of the image. If the image does not exist then Tk_GetImage re‐
98 turns NULL and leaves an error message in interpreter interp's result.
99 When a widget wishes to actually display an image it must call Tk_Re‐
101 drawImage, identifying the image (image), a region within the image to
102 redisplay (imageX, imageY, width, and height), and a place to display
103 the image (drawable, drawableX, and drawableY). Tk will then invoke
104 the appropriate image manager, which will display the requested portion
105 of the image before returning.
106 A widget can find out the dimensions of an image by calling Tk_Size‐
108 OfImage: the width and height will be stored in the locations given by
109 widthPtr and heightPtr, respectively.
110 When a widget is finished with an image (e.g., the widget is being
112 deleted or it is going to use a different image instead of the current
113 one), it must call Tk_FreeImage to release the image instance. The
114 widget should never again use the image token after passing it to
115 Tk_FreeImage. There must be exactly one call to Tk_FreeImage for each
116 call to Tk_GetImage.
117 If the contents or size of an image changes, then any widgets using the
119 image will need to find out about the changes so that they can redis‐
120 play themselves. The changeProc and clientData arguments to Tk_GetIm‐
121 age are used for this purpose. changeProc will be called by Tk when‐
122 ever a change occurs in the image; it must match the following proto‐
123 type:
124 typedef void Tk_ImageChangedProc(
125 ClientData clientData,
126 int x,
127 int y,
128 int width,
129 int height,
130 int imageWidth,
131 int imageHeight);
132 The clientData argument to changeProc is the same as the clientData ar‐
133 gument to Tk_GetImage. It is usually a pointer to the widget record
134 for the widget or some other data structure managed by the widget. The
135 arguments x, y, width, and height identify a region within the image
136 that must be redisplayed; they are specified in pixels measured from
137 the upper-left corner of the image. The arguments imageWidth and im‐
138 ageHeight give the image's (new) size.
139
141 Tk_CreateImageType
142
144 images, redisplay
145Tk 4.0 Tk_GetImage(3)