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| '''But, wait ... There's more !''' There are __two kinds of transparency__ that a wx.Image or wx.Bitmap can have: 1) Every pixel is either completely transparent or completely opaque. This binary transparency is a '''transparency mask'''. 2) Each pixel can have a variable amount of transparency from completely transparent to completely opaque. The amount of transparency each pixel has is defined by a value from 0 to 255. This is '''alpha transparency'''. For example, a GIF file may have a transparency mask, or no transparency at all. A PNG file, however, may have one of a transparency mask, alpha transparency or neither. In comparison, JPG files cannot have any kind of transparency. | '''But, wait ... There's more !''' There are __two kinds of transparency__ that a wx.Image or wx.Bitmap can have: 1) Every pixel is either completely transparent or completely opaque. This binary transparency is a '''transparency mask'''. 2) Each pixel can have a variable amount of transparency that is from completely transparent (alpha value=0) to completely opaque (value=255). The amount of transparency each pixel has is defined by a value from 0 to 255. This is '''alpha transparency'''. For example, a GIF file may have a transparency mask, or no transparency at all. A PNG file, however, may have a transparency mask, alpha transparency or neither. In comparison, JPG files cannot have any kind of transparency. |
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| Reading an image file into a wx.Bitmap : {{{ wxBitmap = wx.EmptyBitmap( 12, 34 ) # Create a bitmap container object wxBitmap.LoadFile( filename, wx.BITMAP_TYPE_ANY ) # Load it with an image |
Creating a wx.Bitmap from an image file : {{{ wxBmap = wx.EmptyBitmap( 1, 1 ) # Create a bitmap container object. The size values are dummies. wxBmap.LoadFile( filename, wx.BITMAP_TYPE_ANY ) # Load it with a file image. }}} Determine whether a bitmap has a mask or alpha transparency : {{{ bmapHasMask = wxBmap.GetMask() # "GetMask()", NOT "HasMask()" ! bmapHasAlpha = wxBmap.HasAlpha() }}} Creating a wx.Image from an image file is just like that for a wx.Bitmap : {{{ wxImg = wx.EmptyBitmap( 1, 1 ) # Create a bitmap container wxImg.LoadFile( filename, wx.BITMAP_TYPE_ANY ) |
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| bitmapHasMask = wxBitmap.GetMask() # "GetMask", NOT "HasMask" ! bitmapHasAlpha = wxBitmap.HasAlpha() }}} Reading an image file into a wx.Image : {{{ wxBitmap = wx.EmptyBitmap( 12, 34 ) # Create a dummy image wxBitmap.LoadFile( filename, wx.BITMAP_TYPE_ANY ) }}} To determine whether the bitmap has a mask or alpha transparency : {{{ imageHasMask = wxImage.HasMask() # "HasMask", NOT "GetMask" ! Egads ... imageHasAlpha = wxImage.HasAlpha() }}} Reading an image file into a Python Image : {{{ pyImage = Image.open( filename ) }}} To check if a PIL image has alpha transparency : {{{ pyImageHasAlpha = pyImage.mode[ -1 ] == 'A' |
imgHasMask = wxImg.HasMask() # "HasMask()", NOT "GetMask()" ! Egads ... imgHasAlpha = wxImg.HasAlpha() }}} Reading an image file into a PIL Image : {{{ import Image pilImage = Image.open( filename ) }}} The PIL open() function automatically determines the file's image type. wxPython will not allow you to drop the "wx.BITMAP_TYPE_ANY" parameter even though it's not needed. Remember that PIL image transparency can only be the alpha kind. To check if a PIL image has transparency : {{{ pilImageHasAlpha = pilImg.mode[ -1 ] == 'A' |
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| imageHasMask = wxImage.HasMask() if wxImage.HasMask() : wxImage.InitAlpha() }}} To handle all the image type conversions while also copying any transparency the following '''ImgConv.py''' module can be used. Make the calls with any flag parameters at their default values, that is, don't even include them in the call parameter list. If you start with a wx.Bitmap or a wx.Image that has either a transparency mask or alpha transparency, these routines will carry over that transparency to a PIL image with alpha. A transparency mask will always be converted into alpha transparency. That is, PIL images can have only have alpha for transparency, never masks. So, when this package converts a PIL image with transparency, the resulting wx.Image or wx.Bitmap will get the PIL image's alpha , never a mask. You can use the flag parameters '''addAlphaLayer''' and '''delAlphaLayer''' to optionally : 1) Create an image with a alpha transparency when a source image had none (addAlphaLayer=True), or conversely, 2) Prevent alpha from automatically being created when the source image has one (delAlphaLayer=True). |
imgHasMask = wxImg.HasMask() if wxImg.HasMask() : wxImg.InitAlpha() }}} To handle all the various image type conversions while also properly copying any transparency the following '''ImgConv.py''' module can be used. Make the calls with any flag parameters at their default values, that is, don't even include them in the call parameter list. If you start with a wx.Bitmap or a wx.Image that has either a transparency mask or alpha transparency, these routines will carry over that transparency to a PIL image with alpha. A transparency mask will always be converted into alpha transparency. PIL images can have only have alpha for transparency, never masks. So, when this package converts a PIL image with transparency, the resulting wx.Image or wx.Bitmap will have alpha transparency, not a mask. You can use the flag parameters '''addAlphaLayer''' and '''delAlphaLayer''' to optionally : 1) Create an image with a alpha transparency when a source image had none (addAlphaLayer=True), or conversely, 2) Prevent alpha from automatically being created in the new image when the source image does has alpha (delAlphaLayer=True). |
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| This module also contains six conversion functions, but it automatically preserves any transparency that is present in the input images: | This module contains six conversion functions. By default it automatically preserves any transparency that is present in the input image. This is usually what is wanted when displaying them in an app. |
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| This module has some functions for extracting and combining masks useful for advanced image manipulation. I've used these for creating free form, non-rectangular wx.Frames with semi-transparent background images overlaid with completely opaque and dynamically changing text. | The '''BitmapManip.py''' module has utility functions for extracting and combining masks useful for advanced image manipulation. Wx.Frames can be created that are free-form non-rectangular with semi-transparent background images overlaid with completely opaque and dynamically changing text. |
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| myWxBitmap = myWxImage.ConvertToBitmap() | myWxBmap = myWxImg.ConvertToBitmap() |
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| myWxBitmap = wxBitmapFromImage( myWxImage ) | myWxBmap = wxBitmapFromImage( myWxImg ) |
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| myStringData = myWxImage.GetData() }}} Returns a Python string of binary data of length (width * height * 3). |
myStrData = myWxImg.GetData() }}} This returns a binary data Python string of of length (width * height * 3). |
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| image = wxImage() image.SetData( pythonStringData ) }}} where pythonStringData is a Python string of binary data of length (width * height * 3). |
wxImg = wx.Image() wxImg.SetData( myStrData ) }}} |
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| . 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. |
. There seem to be some missing wx functions. I'm not sure if these are available at a lower level of abstraction for the C people, but anyway, here's what hopefully will show up some day : wxBitmap to string data : . Must convert to a wx.Image then call GetData(). |
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| To allow for editing of icons, this would be required. | To allow for editing of icons, this would be required. |
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| import Image | import Image # The fundamental PIL function library. Several more with advanced functions are available. |
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| source = Image.open( r"Z:\mcfport\portfoli\full\claire.jpg" ) image = wx.EmptyImage( *source.size ) image.SetData( source.convert( 'RGB' ).tostring() ) # if the image has an alpha channel, you can set it with this line: image.SetAlphaData(source.convert( 'RGBA' ).tostring()[3::4]) bitmap = image.ConvertToBitmap() # or: bitmap = wx.BitmapFromImage( image ) return bitmap }}} Note: If a GIF file with a mask is read, PIL will automatically convert it to alpha transparency. This is suitable for most purposes. |
pilImg = Image.open( r"Z:\mcfport\portfoli\full\claire.jpg" ) # Or: "Z:/mcfport/portfoli/full/claire.jpg" works on MSW platforms wxImg = wx.EmptyImage( *pilImg.size ) # Easier to call than "wx.EmptyImage( pilImg.size[0], pilImg.size[1] )". wxImg.SetData( pilImg.convert( 'RGB' ).tostring() ) wxBmap = wxImg.ConvertToBitmap() # Or: wxBmap = wx.BitmapFromImage( wxImg ) return wxBmap }}} Note: If a GIF file with a mask is read, PIL will automatically convert it to binary-valued alpha transparency. This is usually suitable for display purposes. |
- Images and bitmaps in wxPython are normally created by loading files from disk. Working with the images in memory is also a common task for certain types of application. This recipe set looks at the in-memory manipulation (and particularly the generation) of images for use in wxPython applications.
Table of Contents:
Contents
Converting Between PIL image, wx.Bitmap and wx.Image
- The Image classes I find myself working with most frequently are wx.Image, wx.Bitmap, and PIL Image. Here are functions I use to convert between them, in all combinations. I like to have these broken out as six individual functions with related names because the usage and naming in the wx.Windows API can be confusing. The API also changes relatively frequently. I believe that the older text in this section is outdated, but I haven't had time to go through it. -- Robb Shecter
1 # Tested with wxPython 2.3.4.2 and PIL 1.1.3.
2 import wx
3 import Image # PIL module. Only if you use the PIL library.
4
5 def WxBitmapToPilImage( myBitmap ) :
6 return WxImageToPilImage( WxBitmapToWxImage( myBitmap ) )
7
8 def WxBitmapToWxImage( myBitmap ) :
9 return wx.ImageFromBitmap( myBitmap )
10
11 #-----
12
13 def PilImageToWxBitmap( myPilImage ) :
14 return WxImageToWxBitmap( PilImageToWxImage( myPilImage ) )
15
16 def PilImageToWxImage( myPilImage ):
17 myWxImage = wx.EmptyImage( myPilImage.size[0], myPilImage.size[1] )
18 myWxImage.SetData( myPilImage.convert( 'RGB' ).tostring() )
19 return myWxImage
20
21 # Or, if you want to copy any alpha channel, too (available since wxPython 2.5)
22 # The source PIL image doesn't need to have alpha to use this routine.
23 # But, a PIL image with alpha is necessary to get a wx.Image with alpha.
24
25 def PilImageToWxImage( myPilImage, copyAlpha=True ) :
26
27 hasAlpha = myPilImage.mode[ -1 ] == 'A'
28 if copyAlpha and hasAlpha : # Make sure there is an alpha layer copy.
29
30 myWxImage = wx.EmptyImage( *myPilImage.size )
31 myPilImageCopyRGBA = myPilImage.copy()
32 myPilImageCopyRGB = myPilImageCopyRGBA.convert( 'RGB' ) # RGBA --> RGB
33 myPilImageRgbData =myPilImageCopyRGB.tostring()
34 myWxImage.SetData( myPilImageRgbData )
35 myWxImage.SetAlphaData( myPilImageCopyRGBA.tostring()[3::4] ) # Create layer and insert alpha values.
36
37 else : # The resulting image will not have alpha.
38
39 myWxImage = wx.EmptyImage( *myPilImage.size )
40 myPilImageCopy = myPilImage.copy()
41 myPilImageCopyRGB = myPilImageCopy.convert( 'RGB' ) # Discard any alpha from the PIL image.
42 myPilImageRgbData =myPilImageCopyRGB.tostring()
43 myWxImage.SetData( myPilImageRgbData )
44
45 return myWxImage
46
47 #-----
48
49 def imageToPil( myWxImage ):
50 myPilImage = Image.new( 'RGB', (myWxImage.GetWidth(), myWxImage.GetHeight()) )
51 myPilImage.fromstring( myWxImage.GetData() )
52 return myPilImage
53
54 def WxImageToWxBitmap( myWxImage ) :
55 return myWxImage.ConvertToBitmap()
But, wait ... There's more ! There are two kinds of transparency that a wx.Image or wx.Bitmap can have: 1) Every pixel is either completely transparent or completely opaque. This binary transparency is a transparency mask. 2) Each pixel can have a variable amount of transparency that is from completely transparent (alpha value=0) to completely opaque (value=255). The amount of transparency each pixel has is defined by a value from 0 to 255. This is alpha transparency. For example, a GIF file may have a transparency mask, or no transparency at all. A PNG file, however, may have a transparency mask, alpha transparency or neither. In comparison, JPG files cannot have any kind of transparency.
Reading Image Files
Creating a wx.Bitmap from an image file :
wxBmap = wx.EmptyBitmap( 1, 1 ) # Create a bitmap container object. The size values are dummies.
wxBmap.LoadFile( filename, wx.BITMAP_TYPE_ANY ) # Load it with a file image.Determine whether a bitmap has a mask or alpha transparency :
bmapHasMask = wxBmap.GetMask() # "GetMask()", NOT "HasMask()" !
bmapHasAlpha = wxBmap.HasAlpha()Creating a wx.Image from an image file is just like that for a wx.Bitmap :
wxImg = wx.EmptyBitmap( 1, 1 ) # Create a bitmap container
wxImg.LoadFile( filename, wx.BITMAP_TYPE_ANY )To determine whether the bitmap has a mask or alpha transparency :
imgHasMask = wxImg.HasMask() # "HasMask()", NOT "GetMask()" ! Egads ...
imgHasAlpha = wxImg.HasAlpha()Reading an image file into a PIL Image :
import Image
pilImage = Image.open( filename )The PIL open() function automatically determines the file's image type. wxPython will not allow you to drop the "wx.BITMAP_TYPE_ANY" parameter even though it's not needed. Remember that PIL image transparency can only be the alpha kind. To check if a PIL image has transparency :
pilImageHasAlpha = pilImg.mode[ -1 ] == 'A'
}When PIL reads in a PNG file with a mask, it automatically converts the mask into binary-valued alpha transparency whose values are either 0 for completely transparent or 255 completely opaque. This is usually not what is wanted.
Converting Binary-Valued Alpha Transparency into True (256 values) Alpha Transparency
PIL image transparency can only be the true, 256-valued alpha kind, but a wx.Bitmap and a wx.Image can have either kind. To convert a wx.Image transparency mask in to true alpha transparency :
imgHasMask = wxImg.HasMask()
if wxImg.HasMask() :
wxImg.InitAlpha()To handle all the various image type conversions while also properly copying any transparency the following ImgConv.py module can be used. Make the calls with any flag parameters at their default values, that is, don't even include them in the call parameter list. If you start with a wx.Bitmap or a wx.Image that has either a transparency mask or alpha transparency, these routines will carry over that transparency to a PIL image with alpha. A transparency mask will always be converted into alpha transparency. PIL images can have only have alpha for transparency, never masks. So, when this package converts a PIL image with transparency, the resulting wx.Image or wx.Bitmap will have alpha transparency, not a mask.
You can use the flag parameters addAlphaLayer and delAlphaLayer to optionally : 1) Create an image with a alpha transparency when a source image had none (addAlphaLayer=True), or conversely, 2) Prevent alpha from automatically being created in the new image when the source image does has alpha (delAlphaLayer=True).
This module contains six conversion functions. By default it automatically preserves any transparency that is present in the input image. This is usually what is wanted when displaying them in an app.
WxBitmapFromPilImage() WxImageFromPilImage() WxBitmapFromWxImage() PilImageFromWxImage() WxImageFromWxBitmap() PilImageFromWxBitmap()
The BitmapManip.py module has utility functions for extracting and combining masks useful for advanced image manipulation. Wx.Frames can be created that are free-form non-rectangular with semi-transparent background images overlaid with completely opaque and dynamically changing text.
Conversions Between wx.Image, wx.Bitmap, wx.Cursor, wx.Icon and String Data
wx.Image to wx.Bitmap :
myWxBmap = myWxImg.ConvertToBitmap()
or :
myWxBmap = wxBitmapFromImage( myWxImg )
wxImage to String Data :
myStrData = myWxImg.GetData()
This returns a binary data Python string of of length (width * height * 3).
Convert String Data to a wx.Image :
wxImg = wx.Image() wxImg.SetData( myStrData )
Python string of binary data to a wx.Bitmap : Go through wx.Image to get a wx.Bitmap.
DATA to a wx.Icon : Should be possible, but I don't see an overloaded-constructor name for it.
wx.Icon to wxBitmap :
myWxBitmap = wx.EmptyBitmap( myIcon.GetWidth(), myIcon.GetHeight() ) myWxBitmap.CopyFromIcon( myIcon )
- There seem to be some missing wx functions. I'm not sure if these are available at a lower level of abstraction for the C people, but anyway, here's what hopefully will show up some day :
wxBitmap to string data :
Must convert to a wx.Image then call GetData().
Python string of binary data or wx.Image to wxCursor :
- Should be an overridden constructor available, not yet.
wx.Icon to Python string of binary data or wx.Image :
- To allow for editing of icons, this would be required.
wxCursor to Python string of binary 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.
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). Note the use of the size attribute of the PIL Image to create the empty wxImage object.
1 import Image # The fundamental PIL function library. Several more with advanced functions are available.
2
3 def BitmapFromFile( self ) :
4
5 pilImg = Image.open( r"Z:\mcfport\portfoli\full\claire.jpg" ) # Or: "Z:/mcfport/portfoli/full/claire.jpg" works on MSW platforms
6 wxImg = wx.EmptyImage( *pilImg.size ) # Easier to call than "wx.EmptyImage( pilImg.size[0], pilImg.size[1] )".
7 wxImg.SetData( pilImg.convert( 'RGB' ).tostring() )
8
9 wxBmap = wxImg.ConvertToBitmap() # Or: wxBmap = wx.BitmapFromImage( wxImg )
10 return wxBmap
Note: If a GIF file with a mask is read, PIL will automatically convert it to binary-valued alpha transparency. This is usually suitable for display purposes.
NumPy
This example shows the creation of a bitmap using a NumPy array as the data source. Note that NumPy 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 'uint8' data type for image data in rgb format.
1 import wx, numpy
2
3 def GetBitmap( self, width=32, height=32, colour = (0,0,0) ):
4 array = numpy.zeros( (height, width, 3),'uint8')
5 array[:,:,] = colour
6 image = wx.EmptyImage(width,height)
7 image.SetData( array.tostring())
8 wxBitmap = image.ConvertToBitmap() # OR: wx.BitmapFromImage(image)
9 return wxBitmap
Slicing
NumPy's slicing notation, for our purposes, works 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 )
Examples
This example shows use of NumPy's (extended) slicing notation to alter an in-memory image. Note that the slice notation allows for standard negative-value index semantics. Also note the accomodating nature of the assignment operation. Assigning a three-tuple to a row sets every value in the row, while assigning a list of three-tuples will set each value individually (and raise an error if the number of items is incorrect).
1 import wx, numpy
2
3 def GetBitmap( self, width=32, height=32, colour=(128, 128, 128), border=5, borderColour=(255, 255, 255) ):
4 """
5 Creates a bitmap with a border.
6 """"
7 array = numpy.zeros( (height, width, 3), 'uint8' )
8 array[ border:-border, border:-border, : ] = colour
9 array[ :border, :, : ] = borderColour
10 array[ -border:, :, : ] = borderColour
11 array[ :, :border, :] = borderColour
12 array[ :, -border:, : ] = borderColour
13 image = wx.EmptyImage( width, height )
14 image.SetData( array.tostring() )
15 return image.ConvertToBitmap() # OR: wx.BitmapFromImage( image )
This example creates a horizontal gradient between two colours. Note that NumPy is automatically converting from float to uint8 data type in the assignment to array, because of the slice indexing. Without the indexing, array would just get overwritten to point to a different numpy array instead of assigning data within the existing one.
1 import numpy as np
2
3 def GetBitmap( self, width=640, height=480, leftColour=(255,128,0), rightColour=(64,0,255) ):
4 """
5 Create a horizontal gradient
6 """"
7 array = np.zeros( (height, width, 3), 'uint8' )
8
9 # alpha is a one dimensional array with a linear gradient from 0.0 to 1.0
10 alpha = np.linspace( 0., 1., width )
11
12 # This uses alpha to linearly interpolate between leftColour and rightColour
13 colourGradient = np.outer(alpha, leftColour) + np.outer( (1.-alpha), rightColour )
14
15 # NumPy's broadcasting rules will assign colourGradient to every row of the destination array
16 array[ :, :, : ] = colourGradient
17 image = wx.EmptyImage( width, height )
18 image.SetData( array.tostring() )
19 wxBitmap = wx.BitmapFromImage( image ) # OR: image.ConvertToBitmap()
20 return wxBitmap
Screen Capture
This example captures the client area of a frame to a wxBitmap object (and from there, a file). Note that there is no error checking done here. Should likely use Ok() or something to check each context. I'm not sure what would happen if this were called before the first painting of the screen, likely the context would have the desktop or something in it. Note: code below only captures the client area of the window. Tagore notes that you can get the whole window with a wx.WindowDC and arbitrary parts of the screen with a wx.ScreenDC.
1 def OnSaveToFile( self, event ):
2 context = wx.ClientDC( self )
3 memory = wx.MemoryDC( )
4 x, y = self.ClientSize
5 bitmap = wx.EmptyBitmap( x, y, -1 )
6 memory.SelectObject( bitmap )
7 memory.Blit( 0, 0, x, y, context, 0, 0)
8 memory.SelectObject( wx.NullBitmap)
9 bitmap.SaveFile( 'test.bmp', wx.BITMAP_TYPE_BMP )
A Flexible Screen Capture App
Here's a general screen capture app that first captures the whole primary screen, then captures 4 smaller portions of it. GeneralScreenShotWX.py
1 def ScreenCapture( captureStartPos, captureSize ) :
2 """
3 A general Desktop screen capture.
4
5 My particular monitor configuration:
6 wx.Display( 0 ) refers to the extended Desktop display monitor screen.
7 wx.Display( 1 ) refers to the main Desktop display monitor screen.
8
9 Any particular Desktop screen size is :
10 screenRect = wx.Display( n ).GetGeometry()
11
12 Different wx.Display's in a single system are allowed to have
13 different dimensions.
14
15 """
16
17 # Capture the entire composite Desktop screen by creating a wx.ScreenDC.
18 # This DC is just a tool linked to a copy of the bitmap of the entire Desktop.
19 # The screen's size might be extended by the use of multiple monitors.
20 screenDC = wx.ScreenDC()
21 screenSizeX, screenSizeY = screenDC.Size # The screen's dimensions.
22
23 # The size of the Desktop bitmap area to be returned.
24 captureSizeX, captureSizeY = captureSize
25
26 # Create a new empty (black) destination bitmap with the size of captureSize.
27 captureBmap = wx.EmptyBitmap( captureSizeX, captureSizeY )
28
29 # Create a new DC tool that is associated with this bitmap.
30 memDC = wx.MemoryDC( captureBmap )
31
32 # Configure the upcoming Blit call's position and size parameters
33 # that will be used to copy a portion of the source Desktop bitmap
34 # into the destination bitmap (captureBmap).
35 #
36 # The upper-left coordinate of the screen bitmap portion to be copied.
37 screenStartX, screenStartY = captureStartPos
38
39 # The upper-left destination starting coordinate for the .blit() operation:
40 captureBmapStartX, captureBmapStartY = (0, 0)
41
42 # Copy (blit, "Block Level Transfer") a portion of the screen bitmap
43 # into the capture bitmap.
44 # The bitmap associated with memDC (captureBmap) is the blit destination.
45 # # Blit (copy) parameter(s):
46 memDC.Blit( captureBmapStartX, captureBmapStartY, # Copy to captureBmap starting here.
47 captureSizeX, captureSizeY, # Copy an area this size.
48 screenDC, # Copy from this source DC's bitmap.
49 screenStartX, screenStartY ) # Copy from this start coordinate.
50
51 memDC.SelectObject( wx.NullBitmap ) # Finish using this wx.MemoryDC.
52 # Release captureBmap from memDC.
53 return captureBmap
54
55 #end ScreenCapture def
In the application all five captured wxBitmap objects are saved to PNG files.
The wx.ScreenDC treats the entire Desktop screen as a single seamless conglomerate of all exiting wx.Display() areas. Negative coordinate values relative to the main Desktop screen are allowed. Negative ordinate values must be used to capture any portion of an extension monitor screen to the left of or above the primary monitor screen (the one with the Taskbar). For example, I have two monitors where the extension monitor is configured to be directly above the main monitor. I have set both monitors to 1280x800 resolution. To capture the just the whole extended screen :
1 screenWid = wx.SystemSettings.GetMetric( wx.SYS_SCREEN_X )
2 screenHgt = wx.SystemSettings.GetMetric( wx.SYS_SCREEN_Y )
3 captureSize = (screenWid, screenHgt*2) # Both screens are set to be the same size.
4 wxBitmap = ScreenCapture( startPos, captureSize )
Other wxPython add-on packages can take arbitrarily sized screen shots, too, such as ImageMagick and PIL. Python Imaging Library:
-- Ray Pasco
Write Text to a Bitmap
Writing text into a bitmap is done by creating a context then using the context's DrawText method to do the actual drawing. A simple example:
1 import wx
2
3 def SetDcContext( memDC, font=None, color=None ):
4 if font:
5 memDC.SetFont( font )
6 else:
7 memDC.SetFont( wx.NullFont )
8
9 if color:
10 memDC.SetTextForeground( color )
11
12 #end def
13
14 def WriteTextOnBitmap( text, bitmap, pos=(0, 0), font=None, color=None) :
15 """
16 Simple write into a bitmap doesn't do any checking.
17 """
18 memDC = wx.MemoryDC()
19 SetDcContext( memDC, font, color )
20 memDC.SelectObject( bitmap )
21 try:
22 memDC.DrawText( text, pos[0], pos[1])
23 except :
24 pass
25
26 memDC.SelectObject( wx.NullBitmap )
27
28 return bitmap
29
30 #end def
One of the things you might want to use this for is creating "button labels" for wx.BitmapButtons. The following utility function provides basic centred-text (potentially multi-line) captions for your bitmaps. It also demonstrates the use of the context's GetTextExtent method to perform centring of the text:
1 import wx
2
3 MINIMUMFONTSIZE = 4
4
5 def WriteCaptionOnBitmap( text, bitmap, font=None, margins = (2,2), color=None ):
6 """
7 Write the given caption (text) into the bitmap
8 using the font (or default if not given) with the
9 margins given. Will try to make sure the text fits
10 into the bitmap.
11 """
12 memory = wx.MemoryDC( )
13 font = font or memory.GetFont()
14 textLines = text.split( '\n' )
15 fit = False
16 while not fit:
17 totalWidth=0
18 totalHeight = 0
19 setLines = []
20 for line in textLines:
21 if line and line[-1] == '\r':
22 line = line[:-1]
23
24 width, height = extents = memory.GetTextExtent( line )
25 totalWidth = max( totalWidth, width )
26 totalHeight += height
27 setLines.append( (line, extents))
28 #end for
29
30 if (totalWidth > (bitmap.GetWidth()- 2*margins[0]) or \
31 (totalHeight > (bitmap.GetHeight()- 2*margins[0]) ) :
32
33 size = font.GetPointSize() - 1
34 if size < MINIMUMFONTSIZE:
35 fit = True # will overdraw!!!
36 else:
37 font.SetPointSize( size )
38 memory.SetFont( font )
39 else:
40 fit = True
41 #end if
42
43 #end while
44
45 if not setLines:
46 return bitmap
47
48 centreX, centreY = (bitmap.GetWidth()/2), (bitmap.GetHeight()/2)
49 x, y = centreX-(totalWidth/2), centreY-(totalHeight/2)
50 memory.SelectObject( bitmap )
51 SetMemDcContext( memory, font, color)
52 for line, (deltaX, deltaY) in setLines:
53 x = centreX - (deltaX/2)
54 memory.DrawText( line, x, y,)
55 y += deltaY
56 memory.SelectObject( wxNullBitmap)
57 return bitmap
58
59
60 def SetMemDcContext( memory, font=None, color=None ) :
61
62 if font:
63 memory.SetFont( font )
64 else:
65 memory.SetFont( wx.NullFont )
66
67 if color:
68 memory.SetTextForeground( color )
Since transparency is a bit tricky, here is another example. (Which unlike the above, works for me).
In this example two bitmaps are created. One is completely white (oldPix) the other one completely black (newPix). Then a red box is drawn on the black bitmap. Now the black color in newPix is masked and then newPix is copied over oldPix (the white one). The result is, that only the red box is copied.
1 import wx
2
3 class Test(wx.App):
4 def OnInit(self):
5 oldPix = wx.EmptyBitmap(300, 300)
6 newPix = wx.EmptyBitmap(300, 300)
7 mem = wx.MemoryDC()
8 mem.SelectObject(oldPix)
9 mem.Clear() # The images have to be cleared
10 mem.SelectObject(newPix) # because wxEmptyBitmap only
11 mem.SetBackground(wx.BLACK_BRUSH) # allocates the space
12 mem.Clear()
13
14 # We now have a black and a white image
15 # Next we plot a white box in the middle of the black image
16
17 mem.SetPen(wx.RED_PEN)
18 mem.DrawLines(((100, 200), (100, 100), (200, 100), (200,200), (100,200)))
19
20 mem.SelectObject(oldPix)
21 newPix.SetMask(wxMaskColour(newPix, wx.BLACK))
22 mem.DrawBitmap(newPix, 0, 0, 1)
23
24 oldPix.SaveFile("oldPix.bmp", wx.BITMAP_TYPE_BMP)
25 newPix.SaveFile("newPix.bmp", wx.BITMAP_TYPE_BMP)
26 return True
27
28 app = Test(redirect=False)
29 app.MainLoop()
This is a complete wxPython app, so just run it and have a look at the created Bitmaps oldPix.bmp and newPix.bmp for the results. -- Nikolai Hlubek
PythonMagick (a 16-bit Imaging Library)
Here is a short but complete PythonMagick/wxPython program. The program uses wxPython GUI, loads an image, displays the image, and does a simple image processing operation (threshold). Various conversions between PythonMagick, PIL, and wxPython images are available on the PythonMagick web site.
See the PythonMagick page for a greater description of PythonMagick.
Note that PythonMagick presently only has a Windows installer.
1 from wxPython import wx
2 import PythonMagick
3
4 ID_FILE_OPEN = wx.wxNewId()
5 ID_FILE_EXIT = wx.wxNewId()
6 ID_THRESHOLD = wx.wxNewId()
7
8 class ImagePanel(wx.wxPanel):
9 def __init__(self, parent, id):
10 wx.wxPanel.__init__(self, parent, id)
11 self.image = None # wxPython image
12 wx.EVT_PAINT(self, self.OnPaint)
13
14 def display(self, magickimage):
15 self.image = self.convertMGtoWX(magickimage)
16 self.Refresh(True)
17
18 def OnPaint(self, evt):
19 dc = wx.wxPaintDC(self)
20 if self.image:
21 dc.DrawBitmap(self.image.ConvertToBitmap(), 0,0)
22
23 def convertMGtoWX(self, magickimage):
24 img = PythonMagick.Image(magickimage) # make copy
25 img.depth = 8 # change depth only for display
26 img.magick = "RGB"
27 data = img.data
28 wximg = wx.wxEmptyImage(img.columns(), img.rows())
29 wximg.SetData(data)
30 return wximg
31
32
33 class mtFrame(wx.wxFrame):
34 def __init__(self, parent, ID, title):
35 wx.wxFrame.__init__(self, parent, ID, title, wx.wxDefaultPosition, wx.wxSize(500, 400))
36
37 self.iPanel = ImagePanel(self, -1)
38 self.im = None # Magick image
39
40 ## Construct "File" menu
41 self.menuBar = wx.wxMenuBar()
42 self.menuFile = wx.wxMenu()
43 self.menuFile.Append(ID_FILE_OPEN, "&Open image","")
44 wx.EVT_MENU(self, ID_FILE_OPEN, self.OnOpen)
45 self.menuFile.AppendSeparator()
46 self.menuFile.Append(ID_FILE_EXIT, "E&xit", "")
47 wx.EVT_MENU(self, ID_FILE_EXIT, self.OnExit)
48 self.menuBar.Append(self.menuFile, "&File");
49
50 ## Construct "Process" menu
51 self.menuProcess = wx.wxMenu()
52 self.menuProcess.Append(ID_THRESHOLD, "Threshold", "")
53 wx.EVT_MENU(self, ID_THRESHOLD, self.OnThreshold)
54
55 self.menuBar.Append(self.menuProcess, "&Process")
56 self.SetMenuBar(self.menuBar)
57
58 def OnOpen(self, event):
59 fd = wx.wxFileDialog(self, "Open Image", "", "", "*.*", wx.wxOPEN)
60
61 if fd.ShowModal() == wx.wxID_OK:
62 self.loadImage(fd.GetPath())
63 fd.Destroy()
64
65 def loadImage(self, path):
66 try:
67 self.im = PythonMagick.Image(path)
68 self.iPanel.display(self.im)
69 except IOError:
70 print "can't open the file"
71
72 ##-------------- Process ------------------------
73
74 def OnThreshold(self, event):
75 self.im = self.Threshold(self.im, 0.5)
76 self.iPanel.display(self.im)
77 #self.im.write('d:/threshold.tif')
78
79 def Threshold(self, image, threshold):
80 """
81 Threshold image. Input threshold is normalized (0-1.0)
82 """
83 img = PythonMagick.Image(image) # copy
84 img.threshold(threshold *65535.0)
85 return img
86
87 ##-----------------------------------------------
88
89 def OnCloseWindow(self, event):
90 self.Destroy()
91
92 def OnExit(self, event):
93 self.Close(True)
94
95 #---------------------------------------------------------------------------
96
97 class mtApp(wx.wxApp):
98 def OnInit(self):
99 frame = mtFrame(wx.NULL, -1, "MagickSimple1")
100 frame.Show(True)
101 self.SetTopWindow(frame)
102 return True
103
104 app = mtApp(0)
105 app.MainLoop()
-Bob Klimek 9-23-03
Thanks
Another word of thanks. I used the pil->image with alpha tricks learned from this page.
Anyone know whether there are newer techniques, or is this std? The page was updated 2003 (I think I recall.) (Get hold of me on the fonty python mailing list on google groups.) \d