Remove selection from PNG Image: How to using Lazarus?
lazarus / 39-Graphics

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Boleeman · 2024-12-22 06:09

Hi All.

I came across an interesting CSharp program that removes a user
selection from an image.

Was wondering if anyone has made something similar using Lazarus?
Lazpaint probably does this, but I wanted to make a simple Lazarus
program to do this.

Would probably need to use a TGbrabmp, as a transparent background is
needed.

The program uses a freestyle type selection by mouse dragging the
selected region.
Then there are 2 images presented: one with the selection on a
transparent background and one with the removed bit.
Both of these can then be saved.

I also wanted to vary the selection style with say
1. Freestyle selection
2. Straight line selection.
3. Rectangular selection
4. Polygon Selection.
5. Coloured Line Selection

I also wanted to add another feature to make selected parts
transparent by mouse clicking a selected colour in part of an image.

I may try to convert that CSharp program if this has not been done
before.

Anyhow, I thought I would ask if anything like this exists?

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lainz · 2024-12-22 06:47

Check the bgrabitmap tutorial about using masks. Basically you draw a
Black and white image and mask the other bitmap with that...

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Boleeman · 2024-12-22 07:18

Ok. I Lainz I looked at the Tute at
https://wiki.freepascal.org/BGRABitmap_tutorial_5

So perhaps use TBGRABitmap:

Put a slightly transparent black image ontop of the loaded orginal and
use various shaped selections to choose the visible parts ?

Hmm, will need to investigate that !

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lainz · 2024-12-22 07:26

Black is transparent and white is opaque.

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Boleeman · 2024-12-22 07:48

I made a basic test of masking. It seems to work but now need to
extend this.

Yes, Black is transparent and white is opaque. I get that.
But I wanted to overlay a partly transparent Black image on top of the
other original one, sort of like Onion Skinning in an animation
program, so that I can select only certain regions of the original png
image.

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lainz · 2024-12-22 10:16

Check the same tutorial the part about layers