Provides pointer to direct
access to alpha information
property AlphaScanline[const Index: Integer]: pByteArray;
Description
Some kind of Portable Network Images also provides transparency
information. This allows the images to be draw on the screen with
transparent parts by blending the foreground against the background using
the value provided.
Scanline
property provides direct access to image contents and
AlphaScanline
provides direct access to the image transparency.
It's
important to know that only when
ColorType
is COLOR_RGBALPHA
or COLOR_GRAYSCALEALPHA
AlphaScanline is valid. For other color types, this property will
return nil.
The
data in the pointer received will be always an array of bytes with the
same size as the image width meaning that each byte represents the
transparency for the correspondent position starting from 0 (totally
transparent) to 255 (opaque).
Components
> TPNGObject > Properties > AlphaScanline