IMAQ image rotation not working with all values

[joptimus]

Hi guys,

we have a strange issue with the IMAQ rotate VI from LabVIEW. With some values it doesn't work or gives a wrong result.

For example:

• -2.0 --> rotates -1.9°
• -1.9 --> rotates -1.76°
• -1.8 --> rotates also -1.76°

The rotation values were checked using GIMP measurement tool.

Does this make any sense?

Thanks for your help!

[Bob_Schor]

This is a variation on "Floats vs Integers".  Your Image line is made up of pixels, which have an integer "address" and can thus vary up or down by units of 1 pixel.  So if you have a horizontal line 500 pixels long and lift one end by 1 pixel (the smallest amount you can change it), it will be at an angle of 0.115 degrees, which is as close to 0.1 degrees as it is (mathematically) possible to get.

Bob Schor

[joptimus]

Thanks!

Yet I thought LabVIEW supported subpixel accuracy...?

[AnalogKid2DigitalMan]

Sub-pixel interpolation for measurements using edge finders. It is quite impressive as my latest project has proven to resolve ~0.1um with a native per-pixel resolution of 2.3um/pixel.

-AK2DM