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James Gregory 2013-12-30 18:34:31 +11:00
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43-02.md
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@ -23,7 +23,7 @@ us transparency, where rearward images would show through holes within
and around the edges of images in forward planes. Finally, and most
importantly, it would meet all the criteria needed to allow us to store
each image in a single plane, letting us manipulate the images very
quickly and with no reprogramming of the VGA’s hardware other than the
quickly and with no reprogramming of the VGA's hardware other than the
few **OUT** instructions required to select the plane we want to write
to.
@ -34,7 +34,7 @@ the highest precedence determines the color. The palette RAM settings
for the colors described above are summarized in Table 43.1.
Remember that the 4-bit values coming from display memory select which
palette register provides the actual pixel color. Given that, it’s easy
palette register provides the actual pixel color. Given that, it's easy
to see that the rightmost 1-bit of the four bits coming from display
memory in Table 43.1 selects the pixel color. If the bit from plane 0 is
1, then the color is red, no matter what the other bits are, as shown in
@ -161,11 +161,11 @@ Table 43.1 Palette RAM settings for bit-plane animation.
![](images/43-04.jpg)\
**Figure 43.4**  *How pixel precedence works.*
Seems almost too easy, doesn’t it? Nonetheless, it works beautifully, as
we’ll see very shortly. First, though, I’d like to point out that
there’s nothing sacred about plane 0 having precedence. We could
Seems almost too easy, doesn't it? Nonetheless, it works beautifully, as
we'll see very shortly. First, though, I'd like to point out that
there's nothing sacred about plane 0 having precedence. We could
rearrange the palette register settings so that any plane had the
highest precedence, followed by the other planes in any order. I’ve
highest precedence, followed by the other planes in any order. I've
chosen to make plane 0 the highest precedence only because it seems
simplest to think of plane 0 as appearing in front of plane 1, which is
in front of plane 2, which is in front of plane 3.