Considerations When Using Scaling - Basler acA2040-55 User Manual

AW00123409000
Frequently, scaling involves the rounding of frame dimensions. The rounding
effects will be cumulative when applying a sequence of different scaling factors.
When reversing the scaling, e.g. to return to a previous frame size, the frame
dimensions lost during rounding are not restored. Accordingly, the previous frame
size will not exactly be reached.
You can correct for the cumulative rounding losses by setting the previous frame
size manually. Alternatively, instead of applying one scaling factor immediately
after another, you can in between return to a "reference" frame size, e.g. to full
resolution, and set the frame size manually to correct for rounding errors.
Setting Scaling
You can use the scaling feature by setting the ScalingHorizontal parameter. value from within your
application software by using the Basler pylon API. The following code snippet illustrates using the
API to set the parameter value. The example illustrates setting the width of the current frame to one
half of the original length:
// Set horizontal scaling
camera.ScalingHorizontal.SetValue(0.5);
double d = camera.ScalingHorizontal.GetValue();
You can also use the Basler pylon Viewer application to easily set the parameters.
For more information about the pylon API and the pylon Viewer, see Section 3.1 on

7.10.1 Considerations When Using Scaling

Scaling's Effect on ROI Settings
When you have the camera set to use scaling, keep in mind that the settings for your image region
of interest (ROI) will refer to the rows and columns of the modified frame and not to the physical
rows and columns in the sensor as they normally would. Another way to think of this is by using the
concept of a "virtual sensor".
For example, assume that you are using an acA3800-14um camera with a scaling factor of 0.5
applied to full resolution (3840 × 2748 pixels). In this case, you would act as if you were actually
working with a 1918 column by 1372 row sensor when setting your ROI parameters. The maximum
ROI width would be 219 and the maximum ROI height would be 164. When you set the Offset X
and the Width for the ROI, you will be setting these values in terms of virtual sensor columns. And
when you set the Offset Y and the Height for the ROI, you will be setting these values in terms of
virtual sensor rows and columns.
For more information about the image region of interest (ROI) feature, see Section 7.6 on
Basler ace USB 3.0
Features
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