Compare images

[spacebuddy]

Hi All,

Is there anything in PB that allows you to compare two images to see if
they are identical?

[J. Baker]

If you use Point(), you can compare per pixel. You can even use Plot() to draw hot pink (or something like that) on the second image or even a third, to see the difference.

[wilbert]

If you get the address of the pixel data, you could use CompareMemory.

[spacebuddy]

If you use Point(), you can compare per pixel. You can even use Plot() to draw hot pink (or something like that) on the second image or even a third, to see the difference.

I tried that, but it is to slow for me

[spacebuddy]

If you get the address of the pixel data, you could use CompareMemory.

I am getting the image from the clipboard, so I am not sure how you can get the address?

[J. Baker]

If you use Point(), you can compare per pixel. You can even use Plot() to draw hot pink (or something like that) on the second image or even a third, to see the difference.

I tried that, but it is to slow for me

It shouldn't be. Do all your comparing in the background. Not like where you can visually see it comparing in a window or something. Then when done comparing, then draw the result images so you can visually see it.

[Fred]

Another way is to use DrawingBuffer() and then compare lines by lines with CompareMemory().

[spacebuddy]

I am trying it a different way by trying to get the crc value of the image. This is the
code I am using which does not work

StartDrawing( ImageOutput( ImageHandle ) )
image_data = DrawingBuffer()
StopDrawing()
Length = MemoryStringLength(*image_data)
Result = CRC32Fingerprint(*image_data, Length)

Anyone tell me why this does not work.

Thanks all for the replies.

[infratec]

Hi,

Maybe because you forgot an *
But still than, you can not use MemoryStringLength() since a picture contains 0
And MemorySize() works only with AllocateMemory()

Maybe this works;

Code: Select all

EnableExplicit

Define ImageHandle.i, *Buffer, Pitch.i, Length.i, Result.l

CreateImage(ImageHandle, 300, 200)

StartDrawing(ImageOutput(ImageHandle))
*Buffer = DrawingBuffer()
Pitch = DrawingBufferPitch()
Length = Pitch * ImageHeight(ImageHandle)
Result = CRC32Fingerprint(*Buffer, Length)
StopDrawing()

Debug Hex(Result, #PB_Long)

Bernd

[Fred]

The DrawingBuffer() is invalidated on StopDrawing, so you can't store the pointer and use it after StopDrawing().

[infratec]

Thanks Fred,

I corrected the listing above.

Bernd

[spacebuddy]

Thank you all, everything working now