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Ruslan

Draw objects on canvas and manipulate with them

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Maybe a stupid question but not for me at the moment.

Need a way to draw rectangles on a canvas and then to make it possible to resize, move, delete or clone. That is needed to automate some process of segmentation objects (same kind of objects by rectangles with same aspect ratio) on a bunch of images (>100K).

For now I can draw rectagles on a TImage canvas wthout any questions. But can't figure out how to select that rectangle with mouse, resize it, scale it and move.

Or maybe should I look at shapes?

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Posted (edited)

Yóu can draw like this.

But the Canvas is a raster-based area, which doesn't contain graphical objects.

So the only way would be to re-paint the objects, as you like.

Usually this is done via FrameBuffer bitmaps, where you can do the clearing and drawing, and then
paint the whole frame buffer to the canvas each frame (or when changed).

Edited by Rollo62
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I would not draw directly on the canvas. Use TShapes.

You may also want to have a look at this selection component that is part of FMX:

TSelection

 

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