Declaration

function BlendReg(F, B: TColor32): TColor32;
procedure BlendMem(F: TColor32; var B: TColor32);
procedure BlendMems(F: TColor32; Dst: PColor32; Count: Integer);
function BlendRegEx(F, B: TColor32; M: Cardinal): TColor32;
procedure BlendMemEx(F: TColor32; var B: TColor32; M: Cardinal);
function BlendRegRGB(F, B: TColor32; W: Cardinal): TColor32;
procedure BlendMemRGB(F: TColor32; var B: TColor32; W: Cardinal);
procedure BlendLine(Src, Dst: PColor32; Count: Integer);
procedure BlendLineEx(Src, Dst: PColor32; Count: Integer; M: Cardinal);

Parameters

Parameter	Type	Description
F	TColor32	Foreground pixel color.
B	TColor32	Background pixel color.
M	Cardinal	Master alpha weight or mask value (0..255).
W	Cardinal	Explicit blending weight (0..255).
Src	PColor32	Pointer to the first source foreground pixel in memory.
Dst	PColor32	Pointer to the first destination background pixel in memory.
Count	Integer	Number of contiguous background pixels to blend.

Returns

Type	Description
TColor32	The blended 32-bit ARGB result color.

Description

The Blend* family of functions performs standard alpha blending, compositing a foreground color $F$ onto a background color $B$ using $F$'s alpha channel value $F_a$:

$$Z_{rgb}=F_a\cdot F_{rgb}+(1-F_a)\cdot B_{rgb}$$

The background color $B$ is assumed to be fully opaque ($B_a=255$). If $B$ contains semi-transparent alpha, use Merge instead.

Variant Summary

Variant	Signature	Description
BlendReg	function(F, B: TColor32): TColor32;	Blends foreground $F$ and background $B$ in registers.
BlendMem	procedure(F: TColor32; var B: TColor32);	Blends foreground $F$ directly into memory location $B$.
BlendMems	procedure(F: TColor32; B: PColor32; Count: Integer);	Blends uniform foreground $F$ into Count background pixels starting at $B$.
BlendRegEx	function(F, B: TColor32; M: Cardinal): TColor32;	Register blending with master alpha / mask factor $M$ ($0\dots 255$).
BlendMemEx	procedure(F: TColor32; var B: TColor32; M: Cardinal);	In-memory blending with master alpha / mask factor $M$ ($0\dots 255$).
BlendRegRGB	function(F, B: TColor32; W: Cardinal): TColor32;	Register blending with explicit blend weight $W$ ($0\dots 255$).
BlendMemRGB	procedure(F: TColor32; var B: TColor32; W: Cardinal);	In-memory blending with explicit blend weight $W$ ($0\dots 255$).
BlendLine	procedure(Src, Dst: PColor32; Count: Integer);	Scanline blending of Count source pixels onto destination pixels.
BlendLineEx	procedure(Src, Dst: PColor32; Count: Integer; M: Cardinal);	Scanline blending with master alpha factor $M$.

INFO

All these functions are actually delegates; At startup, Graphics32 binds them to the optimal implementation (Pure Pascal, x86/x64 assembly, or SSE2 vector instructions) supported by the host CPU.

See also

• Merge
• Combine
• Alpha Composition
• Naming Conventions