Tk_FindPhoto
Tk_FindPhoto
NAMESYNOPSIS
ARGUMENTS
DESCRIPTION
PORTABILITY
CREDITS
KEYWORDS
___________________________
NAME
Tk_FindPhoto, Tk_PhotoPutBlock, Tk_PhotoPutZoomedBlock, Tk_PhotoGetImage, Tk_PhotoBlank, Tk_PhotoExpand, Tk_PhotoGetSize, Tk_PhotoSetSize − manipulate the image data stored in a photo image.
SYNOPSIS
#include <tk.h>
Tk_PhotoHandle
Tk_FindPhoto(interp, imageName)
int
│
Tk_PhotoPutBlock(interp, handle, blockPtr, x, y,
width, height,compRule) │
int
│
Tk_PhotoPutZoomedBlock(interp, handle, blockPtr, x,
y, width, height,zoomX, zoomY, subsampleX, subsampleY,
compRule) │
int
Tk_PhotoGetImage(handle, blockPtr)
void
Tk_PhotoBlank(handle)
int
│
Tk_PhotoExpand(interp, handle, width, height)
│
void
Tk_PhotoGetSize(handle, widthPtr, heightPtr)
int
│
Tk_PhotoSetSize(interp. handle, width, height)
│
ARGUMENTS
|
Tcl_Interp *interp (in) |
Interpreter in which image was created and in which error reporting is to be done. | ||
|
const char *imageName (in) |
Name of the photo image. | ||
|
Tk_PhotoHandle handle (in) |
Opaque handle identifying the photo image to be affected. | ||
|
Tk_PhotoImageBlock *blockPtr (in) |
Specifies the address and storage layout of image data. | ||
|
int x (in) |
Specifies the X coordinate where the top-left corner of the block is to be placed within the image. | ||
|
int y (in) |
Specifies the Y coordinate where the top-left corner of the block is to be placed within the image. | ||
|
int width (in) |
Specifies the width of the image area to be affected (for Tk_PhotoPutBlock) or the desired image width (for Tk_PhotoExpand and Tk_PhotoSetSize). | ||
|
int compRule (in) |
Specifies the compositing rule used when combining transparent pixels in a block of data with a photo image. Must be one of TK_PHOTO_COMPOSITE_OVERLAY (which puts the block of data over the top of the existing photo image, with the previous contents showing through in the transparent bits) or TK_PHOTO_COMPOSITE_SET (which discards the existing photo image contents in the rectangle covered by the data block.) | ||
|
int height (in) |
Specifies the height of the image area to be affected (for Tk_PhotoPutBlock) or the desired image height (for Tk_PhotoExpand and Tk_PhotoSetSize). | ||
|
int *widthPtr (out) |
Pointer to location in which to store the image width. | ||
|
int *heightPtr (out) |
Pointer to location in which to store the image height. | ||
|
int subsampleX (in) |
Specifies the subsampling factor in the X direction for input image data. | ||
|
int subsampleY (in) |
Specifies the subsampling factor in the Y direction for input image data. | ||
|
int zoomX (in) |
Specifies the zoom factor to be applied in the X direction to pixels being written to the photo image. | ||
|
int zoomY (in) |
Specifies the zoom factor to be applied in the Y direction to pixels being written to the photo image. |
______________
DESCRIPTION
Tk_FindPhoto 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 image create photo command, or assigned by that command if no name was specified.
Tk_PhotoPutBlock is used to supply blocks of image data to be displayed. The call affects an area of the image of size width x height pixels, with its top-left corner at coordinates (x,y). All of width, height, x, and y must be non-negative. If part of this area lies outside the current bounds of the image, the image will be expanded to include the area, unless the user has specified an explicit image size with the −width and/or −height widget configuration options (see photo(n)); in that case the area is silently clipped to the image boundaries.
The block parameter is a pointer to a Tk_PhotoImageBlock structure, defined as follows:
typedef struct {
unsigned char *pixelPtr;
int width;
int height;
int pitch;
int pixelSize;
int offset[4];
} Tk_PhotoImageBlock;
The pixelPtr field points to the first pixel, that is, the top-left pixel in the block. The width and height fields specify the dimensions of the block of pixels. The pixelSize field specifies the address difference between two horizontally adjacent pixels. Often it is 3 or 4, but it can have any value. The pitch field specifies the address difference between two vertically adjacent pixels. The offset array contains the offsets from the address of a pixel to the addresses of the bytes containing the red, green, blue and alpha (transparency) components. These are normally 0, 1, 2 and 3, but can have other values, e.g., for images that are stored as separate red, green and blue planes.
The compRule parameter to Tk_PhotoPutBlock specifies a compositing rule that says what to do with transparent pixels. The value TK_PHOTO_COMPOSITE_OVERLAY says that the previous contents of the photo image should show through, and the value TK_PHOTO_COMPOSITE_SET says that the previous contents of the photo image should be completely ignored, and the values from the block be copied directly across. The behavior in Tk8.3 and earlier was equivalent to having TK_PHOTO_COMPOSITE_OVERLAY as a compositing rule.
The value given for the width and height parameters to Tk_PhotoPutBlock do not have to correspond to the values specified in block. If they are smaller, Tk_PhotoPutBlock extracts a sub-block from the image data supplied. If they are larger, the data given are replicated (in a tiled fashion) to fill the specified area. These rules operate independently in the horizontal and vertical directions.
Tk_PhotoPutBlock normally returns TCL_OK, though if it cannot allocate │ sufficient memory to hold the resulting image, TCL_ERROR is returned │ instead and, if the interp argument is non-NULL, an error message is │ placed in the interpreter’s result.
Tk_PhotoPutZoomedBlock works like Tk_PhotoPutBlock except that the image can be reduced or enlarged for display. The subsampleX and subsampleY parameters allow the size of the image to be reduced by subsampling. Tk_PhotoPutZoomedBlock will use only pixels from the input image whose X coordinates are multiples of subsampleX, and whose Y coordinates are multiples of subsampleY. For example, an image of 512x512 pixels can be reduced to 256x256 by setting subsampleX and subsampleY to 2.
The zoomX and zoomY parameters allow the image to be enlarged by pixel replication. Each pixel of the (possibly subsampled) input image will be written to a block zoomX pixels wide and zoomY pixels high of the displayed image. Subsampling and zooming can be used together for special effects.
Tk_PhotoGetImage can be used to retrieve image data from a photo image. Tk_PhotoGetImage fills in the structure pointed to by the blockPtr 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. Tk_PhotoGetImage returns 1 for compatibility with the corresponding procedure in the old photo widget.
Tk_PhotoBlank blanks the entire area of the photo image. Blank areas of a photo image are transparent.
Tk_PhotoExpand requests that the widget’s image be expanded to be at least width x height pixels in size. The width and/or height are unchanged if the user has specified an explicit image width or height with the −width and/or −height configuration options, respectively. If the image data are being supplied in many small blocks, it is more efficient to use Tk_PhotoExpand or Tk_PhotoSetSize at the beginning rather than allowing the image to expand in many small increments as image blocks are supplied.
Tk_PhotoExpand normally returns TCL_OK, though if it cannot allocate │ sufficient memory to hold the resulting image, TCL_ERROR is returned │ instead and, if the interp argument is non-NULL, an error message is │ placed in the interpreter’s result.
Tk_PhotoSetSize specifies the size of the image, as if the user had specified the given width and height values to the −width and −height configuration options. A value of zero for width or height does not change the image’s width or height, but allows the width or height to be changed by subsequent calls to Tk_PhotoPutBlock, Tk_PhotoPutZoomedBlock or Tk_PhotoExpand.
Tk_PhotoSetSize normally returns TCL_OK, though if it cannot allocate │ sufficient memory to hold the resulting image, TCL_ERROR is returned │ instead and, if the interp argument is non-NULL, an error message is │ placed in the interpreter’s result.
Tk_PhotoGetSize returns the dimensions of the image in *widthPtr and *heightPtr.
PORTABILITY
In Tk 8.3 and earlier, Tk_PhotoPutBlock and Tk_PhotoPutZoomedBlock had different signatures. If you want to compile code that uses the old interface against 8.4 without updating your code, compile it with the flag -DUSE_COMPOSITELESS_PHOTO_PUT_BLOCK. Code linked using Stubs against older versions of Tk will continue to work.
In Tk 8.4, Tk_PhotoPutBlock, Tk_PhotoPutZoomedBlock, Tk_PhotoExpand and │ Tk_PhotoSetSize did not take an interp argument or return any result │ code. If insufficient memory was available for an image, Tk would │ panic. This behaviour is still supported if you compile your extension │ with the additional flag -DUSE_PANIC_ON_PHOTO_ALLOC_FAILURE. Code │ linked using Stubs against older versions of Tk will continue to work.
CREDITS
The code for the photo image type was developed by Paul Mackerras, based on his earlier photo widget code.
KEYWORDS
photo, image
Opportunity
Personal Opportunity - Free software gives you access to billions of dollars of software at no cost. Use this software for your business, personal use or to develop a profitable skill. Access to source code provides access to a level of capabilities/information that companies protect though copyrights. Open source is a core component of the Internet and it is available to you. Leverage the billions of dollars in resources and capabilities to build a career, establish a business or change the world. The potential is endless for those who understand the opportunity.
Business Opportunity - Goldman Sachs, IBM and countless large corporations are leveraging open source to reduce costs, develop products and increase their bottom lines. Learn what these companies know about open source and how open source can give you the advantage.
Free Software
Free Software provides computer programs and capabilities at no cost but more importantly, it provides the freedom to run, edit, contribute to, and share the software. The importance of free software is a matter of access, not price. Software at no cost is a benefit but ownership rights to the software and source code is far more significant.
Free Office Software - The Libre Office suite provides top desktop productivity tools for free. This includes, a word processor, spreadsheet, presentation engine, drawing and flowcharting, database and math applications. Libre Office is available for Linux or Windows.
Free Books
The Free Books Library is a collection of thousands of the most popular public domain books in an online readable format. The collection includes great classical literature and more recent works where the U.S. copyright has expired. These books are yours to read and use without restrictions.
Source Code - Want to change a program or know how it works? Open Source provides the source code for its programs so that anyone can use, modify or learn how to write those programs themselves. Visit the GNU source code repositories to download the source.
Education
Study at Harvard, Stanford or MIT - Open edX provides free online courses from Harvard, MIT, Columbia, UC Berkeley and other top Universities. Hundreds of courses for almost all major subjects and course levels. Open edx also offers some paid courses and selected certifications.
Linux Manual Pages - A man or manual page is a form of software documentation found on Linux/Unix operating systems. Topics covered include computer programs (including library and system calls), formal standards and conventions, and even abstract concepts.
