How to get interpolationmode value from function

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Hi I have a function where I get an InterpolationMode value from the user:

VB

Public Function EncodeImage(ByVal input As Image,ByVal output As String,Optional interpolation As InterpolationMode = InterpolationMode.HighQualityBicubic) As Image

I can't seem to work out how to actually get the value when it is set though.

What I have tried:

I have tried something like:

VB

If interpolation Then graphicsHandle.InterpolationMode = interpolation

But it doesn't give the value.

Any clues would be much appreciated. Thanks!

Posted 6-Jun-18 13:34pm

Floodlight

Updated 6-Jul-18 8:37am

Nelek

v2

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phil.o 7-Jun-18 1:33am

Get the value from where? Interpolation mode is only used by Graphics objects when images are to be scaled or rotated; it is not saved in the image itself.
So, whether you use it in the function where it has been passed as a parameter, or you store it in a global variable if you want to remember it for further operations.

The context in which you want to retrieve this value is unclear.

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User 13204940 · Answer 1 · 2018-07-06T05:11:00

First of all, this can be improved by removing ByVal, as it's the default anyway:

VB

Public Function EncodeImage(ByVal input As Image,ByVal output As String,Optional interpolation As InterpolationMode = InterpolationMode.HighQualityBicubic) As Image

VB

Public Function EncodeImage(input As Image, output As String, Optional interpolation As InterpolationMode = InterpolationMode.HighQualityBicubic) As Image

This could also be logically improved:

VB

If interpolation Then graphicsHandle.InterpolationMode = interpolation

VB

graphicsHandle.InterpolationMode = interpolation

As well as being less efficient, the first one would cause an error because you're comparing an InterpolationMode to true/false, and it cannot be compared as such.

If you're trying to set the InterpolationMode of something and it's been passed as the parameter of the function, as you've got set up already, you can just do the above to use it;

VB

graphicsHandle.InterpolationMode = interpolation

What you may be confused about is the Optional keyword. It means you can choose to specify a value which overrides the default value, or you can leave it, and the default is used.

This means you can both of the following scenarios:

VB

Dim myImg As New Bitmap()
Dim img As Bitmap = EncodeImage(myImg, "this is the output") ' interpolation left blank so it will default to InterpolationMode.HighQualityBicubic

VB

Dim myImg As New Bitmap()
Dim img As Bitmap = EncodeImage(myImg, "this is the output", InterpolationMode.SomethingElse)