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

Using dynamic bitmaps (wxBitmapFromData)

• Using device contexts to write into wxBitmaps

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 user 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?)