Method Reference (COM)

PixelChecksum

Generates a checksum for a region of pixels.

PixelChecksum left, top, right, bottom [, step]

 

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 checksumming 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.

 

Return Value

Returns the checksum value of the region.

 

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.

 

Related

PixelChecksum, PixelGetColor, PixelCoordMode (Option), PixelSearch

 

Example

Set oAutoIt = WScript.CreateObject("AutoItX3.Control")

' Get initial checksum
checksum = oAutoIt.PixelChecksum(0,0, 50,50)