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Figure 7-12, Color key and alpha blending logic – AMD Geode SC3200 User Manual

Page 324

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324

AMD Geode™ SC3200 Processor Data Book

Video Processor Module

32581C

Figure 7-12. Color Key and Alpha Blending Logic

Color register

enabled for this

window

“Graphics

2

inside Video”

is enabled

Cursor color

key matches

graphics value

Pixel outside

the video

window

No

Yes

Use selected cur-

sor color for pixel

No

No

Pixel value

3

matches

normal color

key

Yes

No

Blend graphics

values and video

values using the

alpha value for

this window

Pixel value

3

matches

normal color

key

No

Use graphics

value for this pixel

Yes

Yes

Replace the value

with the color

register value

Yes

Start

Notes:

1)

Alpha window should not be placed outside of the video window.

2)

“Graphics inside Video” is enabled via bit GFX_INS_VIDEO in the Video De-interlacing and Alpha Control register
(F4BAR0+Memory Offset 4Ch[8]).

3)

The “Pixel Value” refers to either the Video value or the Graphics value, depending on the setting of bit COLOR_CHROMA_SEL
in the Display Configuration register (F4BAR0+Memory Offset 04h[20]).

Yes

Use graphics

value for this pixel

Use video value

for this pixel

Yes

COLOR_CHROMA

_SEL = 1

No

No

No

Yes

Use graphics

value for this pixel

Use video value

for this pixel

No

Yes

Yes

No

Pixel inside

1

alpha window

COLOR_CHROMA

_SEL = 1

COLOR_CHROMA

_SEL = 1