SH7205 Datasheet, PDF (1444/1904 Pages) Renesas Technology Corp – Renesas 32-Bit RISC Microcomputer SuperHTM RISC engine Family / SH7200 Series

Section 26 2D Graphics Engine (2DG)
(a) Blending
The blending for the synthesis using two planes is performed according to a general formula,
based on the following algorithm irrespective of the order in which the color value Cb and α value
α b of the background plane and the color value Cf and α value α f of the front plane: (C(i): an
offset value if Cpout: color value after blending, and Apout: α value after blending):
Cpout = Mf * (Cf − C(i)) + (1 − Af) * Mb * (Cb − C(i)) + C(i)
Apout = 1 − (1 − Af) * (1 − Ab)
Background plane
Color value = Cb, α value = αb
Front plane
Color value = Cf, α value = αf
Synthesized plane
Color value = Cpout, α value = Apout
Figure 26.21 Blending for Synthesis using Two Planes
provided
if the front plane is premultiplied, Mf = 1, Cf = Cpf
if the front plane is non-premultiplied, Mf = Af, Cf = Cf
if the background plane is premultiplied, Mb = 1, Cb = Cpb
if the background plane is non-premultiplied, Mb = Ab, Cb = Cb
The diagram below shows the relationship between graphic synthesis planes:
Background plane
Moving picuture plane
Color value = Cv, α value = αv = 1
Graphic plane
Color value = Cz, α value = αz
Synthetic output
Color value = Cp
Character plane
Color value = Cm, α value = αm
Front plane
Output plane (after synthesis)
Color value = Cgout
α value = αgout
Figure 26.22 Relationship between Graphic Synthesis Planes
Rev. 1.00 Mar. 25, 2008 Page 1412 of 1868
REJ09B0372-0100