TImage32.PaintTo draws "fancy" background

[andersmelander]

          Potentiel bug in `TImage32.PaintTo` in the code of background generation , 

graphics32/Source/GR32.ImageFormats.PSD.pas

Line 461 in 89b9c21

AImage.PaintTo(BackgroundBitmap, BackgroundBitmap.BoundsRect);

As I know transparency tiles are painted to mark presence of alpha channel, and reseved for purly internal use and shouldn't be painted in the external Bitmap32 :

I think it's important to disable dmBlend DrawMode in TImage32.Bitmap before exportation

Originally posted by @lamdalili in #240 (comment)

[andersmelander]

As I know transparency tiles are painted to mark presence of alpha channel, and reseved for purly internal use and shouldn't be painted in the external Bitmap32

Yes, that's a bug.
The bug is that the PST_CLEAR_BACKGND paint stage is marked as both a designtime- and a runtime-stage. It should only be marked as a design-time stage. That way it will not be used in PaintTo.

Additionally, the PST_CLEAR_BUFFER paint stage isn't created by default. As far as I can see there's no reason for it to be used when the PST_CLEAR_BACKGND stage is used because PST_CLEAR_BACKGND will completely cover the visible background. Therefore PST_CLEAR_BUFFER can be marked as a run-time paint stage. This way the two paint stages will be mutually exclusive and will not conflict.

I can see that there's some functionality missing in TCustomImage32 with regard to the flattened bitmap produced by PaintTo; It is currently not possible to create a semitransparent flattened bitmap because the background is always opaque with Alpha=255. The reason is that the color of the background is specified with a regular TColor (no alpha) and not a TColor32 (with alpha). I will create a separate issue for that.

I think it's important to disable dmBlend DrawMode in TImage32.Bitmap before exportation

Why?

[andersmelander]

the PST_CLEAR_BUFFER paint stage isn't created by default.

This is documented behavior (see: ExecClearBuffer) but that doesn't mean that it can't be changed.

[andersmelander]

I confused Delphi IDE design-/run-time with application design-/run-time in my last commit so I have deleted the commit.

I will need to extend the paint stage record so it's possible to differentiate between the three possible draw modes:

• Design-time
• Run-time with "stuff" (fancy background)
• Run-time without "stuff" (basically just the image data).

[lamdalili]

Why?

Setting TImage32.Bitmap DrawMode to dmOpaque hides Paint Stages before PST_DRAW_BITMAP and paints corretely the contenent of TImage32, maybe it's not the best solution but actually gives the expected image. I think the issue is due to the "recenly" internal styles designed for the background and should be disabled when entring in PaintToMode.

graphics32/Source/GR32_Image.pas

Line 732 in a1f0140

DefaultCheckersColors: array[TBackgroundCheckerStyle] of TBackgroundOptions.TCheckersColors =

[andersmelander]

Setting TImage32.Bitmap DrawMode to dmOpaque hides Paint Stages before PST_DRAW_BITMAP

I see. IMO that is just a workaround. I would rather fix the problem so we don't need workarounds.