Core Function PixelChecksum

PixelChecksum ( <left>, <top>, <right>, <bottom>, <step>, <hwnd> )

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");

$hWnd = WinGetHandle("Calc", "");
$coord = PixelChecksum( 0, 0, 30, 30, $hWnd );
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!");