Trans
Parameter to the `Put` graphics statement which selects transparent background as the blitting method
Syntax
`
Put [ target, ] [ STEP ] ( x,y ), source [ ,( x1,y1 )-( x2,y2 ) ], Trans
`
Parameters
`Trans`
Required.
Description
`Trans` selects transparent background as the method for blitting an image buffer. This is similar to the `PSET` method, but pixels containing the mask color are skipped.
For 8-bit color images, the mask color is palette index 0. For 16/32-bit color images, the mask color is Magenta, which is `RGB(255, 0, 255)`. The alpha value is ignored when checking for the mask color in 32-bit images.
Note: for 32-bit images, the alpha value of pixels may be changed to 0. This is for efficiency reasons. To preserve the alpha values, a custom blender may be used, as in the second example below.
Example
`
'' set up a screen: 320 * 200, 16 bits per pixel
ScreenRes 320, 200, 16
'' set up an image with the mask color as the background.
Dim img As Any Ptr = ImageCreate( 32, 32, RGB(255, 0, 255) )
Circle img, (16, 16), 15, RGB(255, 255, 0), , , 1, f
Circle img, (10, 10), 3, RGB( 0, 0, 0), , , 2, f
Circle img, (23, 10), 3, RGB( 0, 0, 0), , , 2, f
Circle img, (16, 18), 10, RGB( 0, 0, 0), 3.14, 6.28
'' Put the image with PSET (gives the exact contents of the image buffer)
Draw String (110, 50 - 4), "Image put with PSET"
Put (60 - 16, 50 - 16), img, PSet
'' Put the image with TRANS
Draw String (110, 150 - 4), "Image put with TRANS"
Put (60 - 16, 150 - 16), img, Trans
'' free the image memory
ImageDestroy img
'' wait for a keypress
Sleep
`
`
Function trans32 ( ByVal source_pixel As ULong, ByVal destination_pixel As ULong, ByVal parameter As Any Ptr ) As ULong
'' returns the source pixel
'' unless it is &hff00ff (magenta), then return the destination pixel
If (source_pixel And &hffffff) <> &hff00ff Then
Return source_pixel
Else
Return destination_pixel
End If
End Function
'' set up a screen: 320 * 200, 16 bits per pixel
ScreenRes 320, 200, 32
'' set up an image with the mask color as the background.
Dim img As Any Ptr = ImageCreate( 32, 32, RGB(255, 0, 255) )
Circle img, (16, 16), 15, RGB(255, 255, 0), , , 1, f
Circle img, (10, 10), 3, RGB( 0, 0, 0), , , 2, f
Circle img, (23, 10), 3, RGB( 0, 0, 0), , , 2, f
Circle img, (16, 18), 10, RGB( 0, 0, 0), 3.14, 6.28
'' Put the image with PSET (gives the exact contents of the image buffer)
Draw String (110, 50 - 4), "Image put with PSET"
Put (60 - 16, 50 - 16), img, PSet
'' Put the image with TRANS
Draw String (110, 100 - 4), "Image put with TRANS"
Put (60 - 16, 100 - 16), img, Trans
'' Put the image with TRANS
Draw String (110, 150 - 4), "Image put with trans32"
Put (60 - 16, 150 - 16), img, Custom, @trans32
'' free the image memory
ImageDestroy img
'' wait for a keypress
Sleep
`
Differences from QB

- New to FreeBASIC

See also

- `Put (Graphics)`
- `Custom`