B4J Question [Solved] How to copy a part of a Canvas onto the same Canvas.

[klaus]

I want to copy a part of a Canvas to another place of the same Canvas.
In B4A I use Canvas.DrawBitmap(Canvas.Bitmap, SourceRectange, DestinationRectangle).
In B4J I have two problems:
- DrawImage has no source rectangle to get a part of the source image.
- Canvas has no Image propety, how can I get the image from the Canvas and better a part of it?

The question is related to to this thread.
I want to move the 59 lower rows one row up.
This is done, in B4A, with cvsGraph.DrawBitmap(cvsGraph.Bitmap, rectMoveSource, rectMoveDest).

 

[Daestrum]

Off the top of my head I guess you would need to
a) grab a snapshot of the canvas ( look at snapshotParameters setViewport not inbuilt snapshot)
b) write back to the canvas object (drawimage) allowing for the 1 line missing at bottom

 

[klaus]

Thank you, that's what I am currently lookin at.
Not finished studying.

 

[sorex]

this works fine...

just make sure it's added to the rootpanel or it won't work.

Dim c As Canvas
Dim i As Image
i.Initialize(File.DirAssets,"image.png")
c.Initialize("")
Form1.RootPane.AddNode(c,0,0,100,100)
c.DrawImage(i,0,0,100,100)
c.DrawImage2(c.Snapshot,0,0,20,100,50,0,20,100)

 

[klaus]

Thank you very much.
I'm afraid I hadn't seen the forest for the trees !

 

[Derek Johnson]

Does this technique not degrade the details of the image, when used like this?
Having just read your earlier thread about aliaising, it is probably the DrawImage that may blur the result.

I am trying to do a similar thing with bar codes written to a canvas, and I am finding that some blurring is taking place when I re-write them with DrawImage.

 

[klaus]

No, I used it in this project without any blurr.
The blurr problem I was reporting HERE was solved and explained at the end of the thread.