WorkingWithImages

Formats and Conversions

• Conversions among wxImage, wxBitmap, wxCursor, wxIcon and DATA

  • wxImage to wxBitmap --  myWxImage.ConvertToBitmap() 

    wxImage to DATA --  myWxImage.GetData()  returning a string in width * height * 3 format

    DATA to wxImage --  image = wxImage(); image.SetData( data )  where data is a Python string of length width * height * 3.

    DATA to wxBitmap -- ??? Should be  wxBitmapFromData  DATA to wxIcon -- Should be possible, but I don't see an overloaded-constructor name for it.

    wxIcon to wxBitmap --  bitmap = wxEmptyBitmap( icon.GetWidth(), icon.GetHeight()); bitmap.CopyFromIcon( icon ) 

  There seem to be some missing functions, not sure if these are available at a lower level of abstraction for the C peoples, but anyway, here's what hopefully will show up some day:
  • wxBitmap to DATA or wxImage -- Probably the most critical missing item, currently you have to use "save to file" then load the bitmap back from disk using a wxImage. DATA or wxImage to wxCursor -- Should be an overridden constructor available, not yet. wxIcon to DATA or wxImage -- To allow for editing of icons, this would be required. wxCursor to DATA or wxImage -- Again, to allow for editing cursors. Would also need methods to get the current hot spot. wxImage to wxIcon -- See DATA to wxIcon above, either one would be fine, but would be nice to have the complete set.

Dynamic Bitmaps

• TODO: Using device contexts to write into wxBitmaps (text, lines, other bitmaps, etceteras) TODO: Screen capture???

PIL (Python Imaging Library)

• PIL can be used with wxPython if image processing services are required beyond loading the formats built into wxPython. DATA formatted strings can be created from PIL Image objects using the .convert and .tostring methods (as show in the example below).

        def GetBitmap( self ):
                import Image
                source = Image.open( r"Z:\mcfport\portfoli\full\claire.jpg", 'r')
                image = apply( wxEmptyImage, source.size )
                image.SetData( source.convert( "RGB").tostring() )
                return image.ConvertToBitmap()

Numeric Python

• This example shows the creation of a bitmap using a Numeric Python array as the data source. Note that Numeric uses reversed column-row ordering compared to wxPython, so you'll need to make sure that you generate images using height, width, not width, height coordinates. Also note the use of the 'c' data type for image data in rgb format.

        def GetBitmap( self, width=32, height=32, colour = (0,0,0) ):
                array = Numeric.zeros( (height, width, 3),'c')
                array[:,:,] = colour
                image = wxEmptyImage(width,height)
                image.SetData( array.tostring())
                return image.ConvertToBitmap()

• This example shows use of Numeric's (extended) slicing notation to alter the in-memory image. This slicing notation, for our purposes, goes as follows:

   [ rowStart: rowEnd, columnStart: columnEnd, colourPlanes ] 

  To assign a single colour to the entire image:  array[:,:] = (r,g,b)  . To assign a value to the entire red bit plane:  array[:,:,0] = 255  . To assign a colour to the first row:  array[ 0 ] = (r,g,b )  .

        def GetBitmap( self, width=32, height=32, colour = (128,128,128), border=5, borderColour=(255,255,255) ):
                array = Numeric.zeros( (height, width, 3),'c')
                array[border:-border,border:-border,:] = colour
                array[:border,:,:] = borderColour
                array[-border:,:,:] = borderColour
                array[:,:border,:] = borderColour
                array[:,-border:,:] = borderColour
                image = wxEmptyImage(width,height)
                image.SetData( array.tostring())
                return image.ConvertToBitmap()

Drawing Bitmaps to Screen/Printer Contexts

• This is basically covered in the demo, but it's part of the topic.

Masks and Transparency/Alpha

• Bitmap masks (from the demo) Alpha-blending (is this even possible?)