How to erase a part of a picture ?

[louis]

Hi,
I would like to replace a part of the picture to a transparent part, without anything.
Is it needed to use DrawImageTransparency ?

[Loïc]

Hi,

Here a sample to make an area of an image transparent:

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Call Imaging1.SetROI(10, 10, 100, 100)
Call Imaging1.SwapColorEx(0, 0, 0)

Let me know if it is not clear enough.

With best regards,

Loïc

[louis]

The height and width values in SetROI were too large, so that nothing is done in that case.

Could you explain why SwapColorEx 0,0,0 (0 as source color, 0 as target color and 0 as threshold) produces transparency ?

[Loïc]

Hi,

The height and width values in SetROI were too large, so that nothing is done in that case.

Of course, I was unable to guess the region you have to process. I gave you a sample of a rectangle with 100 pixels of with & height starting at coordinate (10, 10). Just change these parameters to do what you want...

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Could you explain why SwapColorEx 0,0,0 (0 as source color, 0 as target color and 0 as threshold) produces transparency ?

0 is the black color with full transparency (or ARGB(0,0,0,0)).
In the sample I simply asked to replace all pixel into the ROI by the color ARGB(0,0,0,0).

Kind regards,

Loïc

[louis]

The "problem" was solved (mentioned in the subject). I just said that we have to put values not greater than the width/heigth. In my example, I erase a part up to the right. So, it is necessary to enter the width instead of a greater value. So, no problem ! That's fully Ok.

[louis]

During the creation of a pdf file, I would like to transform the white background color of an image to a transparent background. SwapColorEx 0, 0, 0 produces black background.

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        GDIA.PdfNewPdf(path, "", "", "", "") Then
        GDIA.PdfSetMeasurementUnits (2) ' cm
        ImageA = GDIa.PdfAddImageFromGdPictureImage(GDVA.GetNativeImage)       

        GDIB.CloseNativeImage
        GDIB.SetNativeImage (GDVB.GetNativeImage)       
        GDIB.SwapColorEx 0, 0, 0
        ImageB = GDIB.PdfAddImageFromGdPictureImage(GDIB.GetNativeImage)

        Call GDIA.PdfDrawImage(ImageB, 0, 0, width, height)