Paste using source and destination transparencies

wxPython Users
1

How can I get wx to accomplish this Pil method:

`pil1.paste( pil2, # image to paste into pil1 (pil1 has its
own mask)

        (0, 0),     # U-L offset into pil1

        pil2 )      # use pil2's transparency layer as a mask for

pasting.

`

I’ve tried every settings combination for dc.Blit() possible with no
success.

See attached file imagefile_combined_with_masks.png

Sample code, source and resultant images are attached.

Thanks in advance

imagefile_combined_with_masks.zip (5.48 KB)

2

There are likely other ways, but this is the first that popped into my head, and it works:

import wx

app = wx.App(False)

i1 = wx.Bitmap( 'imagefile1.png' )
i2 = wx.Bitmap( 'imagefile2.png' )
i3 = wx.EmptyBitmap(i1.Size.width, i1.Size.height)

dc = wx.MemoryDC(i3)
MASK = (0,0,1) # just an unused color
dc.SetBackground(wx.Brush(MASK))
dc.Clear()
dc.DrawBitmap(i1, 0, 0, True)
dc.DrawBitmap(i2, 0, 0, True)
del dc

i3.SetMaskColour(MASK)
i3.SaveFile('wxcombined.png', wx.BITMAP_TYPE_PNG)

···

On 6/12/10 7:18 PM, Ray Pasco wrote:

How can I get wx to accomplish this Pil method:

pil1.paste( pil2, # image to paste into pil1 (pil1 has its own mask)
(0, 0), # U-L offset into pil1
pil2 ) # use pil2's transparency layer as a mask for pasting.

I've tried every settings combination for dc.Blit() possible with no
success.
See attached file imagefile_combined_with_masks.png

Sample code, source and resultant images are attached.

Thanks in advance

--
Robin Dunn
Software Craftsman

3

There seems to be a "chicken and egg problem" in trying to define an
unused color:

To pick an unused color the final bitmap must be formed, but this
"unused color" must be defined *before* drawing the final bitmap in
order to define the mask color !

Can the transparency in the original image files be used to form the
final transparency mask and avoid this poultry problem ?

···

On Jun 14, 10:21 pm, Robin Dunn <ro...@alldunn.com> wrote:

On 6/12/10 7:18 PM, Ray Pasco wrote:

> How can I get wx to accomplish this Pil method:

> pil1.paste( pil2, # image to paste into pil1 (pil1 has its own mask)
> (0, 0), # U-L offset into pil1
> pil2 ) # use pil2's transparency layer as a mask for pasting.

> I've tried every settings combination for dc.Blit() possible with no
> success.
> See attached file imagefile_combined_with_masks.png

> Sample code, source and resultant images are attached.

> Thanks in advance

There are likely other ways, but this is the first that popped into my
head, and it works:

import wx

app = wx.App(False)

i1 = wx.Bitmap( 'imagefile1.png' )
i2 = wx.Bitmap( 'imagefile2.png' )
i3 = wx.EmptyBitmap(i1.Size.width, i1.Size.height)

dc = wx.MemoryDC(i3)
MASK = (0,0,1) # just an unused color
dc.SetBackground(wx.Brush(MASK))
dc.Clear()
dc.DrawBitmap(i1, 0, 0, True)
dc.DrawBitmap(i2, 0, 0, True)
del dc

i3.SetMaskColour(MASK)
i3.SaveFile('wxcombined.png', wx.BITMAP_TYPE_PNG)

--
Robin Dunn
Software Craftsmanhttp://wxPython.org

4

[[ This group prefers bottom-posting. Top Posting and Bottom Posting ]]

There seems to be a "chicken and egg problem" in trying to define an
unused color:

To pick an unused color the final bitmap must be formed, but this
"unused color" must be defined *before* drawing the final bitmap in
order to define the mask color !

You could convert the source bitmaps to wx.Image and use FindFirstUnusedColour or get the colour it is already using to represent the mask with GetMaskRed|Green|Blue.

Can the transparency in the original image files be used to form the
final transparency mask and avoid this poultry problem ?

Yes, something like this would probably work:

* Create a wx.Region for each of the source bitmaps using the bimap's mask, using wx.RegionFromBitmap.

* Add one region to the other with region1.UnionRegion(region2)

* Convert the result to a wx.Bitmap with region1.ConvertToBitmap()

* Create a wx.Mask from that bitmap and assign it to the bitmap that holds the results of the drawing, with SetMask.

···

On 6/15/10 7:20 AM, WinCrazy wrote:

--
Robin Dunn
Software Craftsman