Core Function PixelChecksum
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| − | PixelChecksum ( <left>, <top>, <right>, <bottom>, <step> ) | + | PixelChecksum ( <left>, <top>, <right>, <bottom>, <step>, <hwnd> ) |
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Default is 1. | Default is 1. | ||
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| + | ==== hwnd ==== | ||
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| + | Optional; Window handle to be used. | ||
=== Return Value === | === Return Value === | ||
Revision as of 20:15, 11 December 2011
PixelChecksum ( <left>, <top>, <right>, <bottom>, <step>, <hwnd> )
Contents |
Description
Generates a checksum for a region of pixels.
Parameters
left
left coordinate of rectangle.
top
top coordinate of rectangle.
right
right coordinate of rectangle.
bottom
bottom coordinate of rectangle.
step
Optional; Instead of searching each pixel use a value larger than 1 to skip pixels (for speed). E.g. A value of 2 will only check every other pixel.
Default is 1.
hwnd
Optional; Window handle to be used.
Return Value
Success: Returns the checksum value of the region.
Failure: Returns -1 if anything goes wrong.
Remarks
Performing a checksum of a region is very time consuming, so use the smallest region you are able to reduce CPU load. On some machines a checksum of the whole screen could take many seconds!
A checksum only allows you to see if "something" has changed in a region - it does not tell you exactly what has changed.
When using a step value greater than 1 you must bear in mind that the checksumming becomes less reliable for small changes as not every pixel is checked.
See "PixelCoordMode" in Opt
Example
$coord = PixelChecksum( 200, 200, 220, 220 ); println("Checksum is $coord");
// Wait until something changes in the region 0,0 to 50,50 // Get initial checksum $checksum = PixelChecksum(0,0, 50,50); // Wait for the region to change, the region is checked every 100ms to reduce CPU load While ($checksum == PixelChecksum(0,0, 50, 50)) Sleep(100); MsgBox("Something in the region has changed!");
