BlendFunc

Action

Specify pixel arithmetic.

 

 

Syntax

BlendFunc  src, dst 

 

 

Remarks

src	Specifies how the source blending factor is computed. One of ZERO, ONE, SRC_ALPHA,DST_ALPHA,ONE_MINUS_SRC_ALPHA or ONE_MINUS_DST_ALPHA.
dst	Specifies how the destination blending factor is computed, One of ZERO, ONE, SRC_ALPHA,DST_ALPHA,ONE_MINUS_SRC_ALPHA or ONE_MINUS_DST_ALPHA.

 

The blend function controls how new color values are combined with the values already in the color buffer.

Given a pixel value source and a previous value in the color buffer destination, the computed color is:

 

source × src + destination × dst

 

for each color channel: red, green, blue and alpha.

 

For more details please refer to the FT800 Series Programmer Guide.PDF from FTDI.

 

See also

Color_A

 

 

Example

' Pseudocode
 
' The default blend function of (SRC_ALPHA, ONE_MINUS_SRC_ALPHA) causes drawing 
' to overlay the destination using the alpha value
Begin_G BITMAPS
Vertex2II 50, 30, 31, &H47
Color_A 128 
Vertex2II 60, 40, 31, &H47

 
' A destination factor of zero means that destination pixels are not used
Begin_G BITMAPS
BlendFunc SRC_ALPHA, ZERO
Vertex2II 50, 30, 31, &H47
Color_A 128 

Vertex2II 60, 40, 31, &H47

 
' Using the source alpha to control how much of the destination to keep
Begin_G BITMAPS
BlendFunc ZERO, SRC_ALPHA

Vertex2II 60, 40, 31, &H47

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