Added more screenshots 3, 4, 5, 6, 7

This commit is contained in:
michaelangel007 2016-01-10 15:23:23 -08:00
parent ad16fe365f
commit 7921d82954
6 changed files with 34 additions and 5 deletions

View File

@ -296,6 +296,8 @@ Enter in:
And we see the correct: `\` And we see the correct: `\`
![Screenshot 3](pics/hgrfont_03.png?raw=true)
### Half-pixel shift ### Half-pixel shift
Fourth, we mentioned above that when we entered in $80 that the Apple didn't display any pixels for this byte. This is because the Apple uses the high-bit as a flag to shift that group of 7 pixels over HALF a pixel. (Yes, half a pixel.) This means the monochrome *effective* resolution is a pseudo 560x192. We can't individually access every 560 pixels, only part of them so it is not a "true" 560 resolution. :-( What this means in practice is that we can use this half-pixel shift / byte to get very smooth slopes for Y, etc. :-) Fourth, we mentioned above that when we entered in $80 that the Apple didn't display any pixels for this byte. This is because the Apple uses the high-bit as a flag to shift that group of 7 pixels over HALF a pixel. (Yes, half a pixel.) This means the monochrome *effective* resolution is a pseudo 560x192. We can't individually access every 560 pixels, only part of them so it is not a "true" 560 resolution. :-( What this means in practice is that we can use this half-pixel shift / byte to get very smooth slopes for Y, etc. :-)
@ -310,16 +312,43 @@ For example this will give us a "sharp" `Y`:
3700:8 3700:8
3B00:8 3B00:8
If we change the 2nd and 4th scan line to: ![Screenshot 4](pics/hgrfont_04.png?raw=true)
2700:92 If we change the 2nd and 4th scan line to use this half-pixel shift we can't just set the high bit as we won't get quite the correct image:
2F00:8C
We'll get a "smooth" `Y`. Enter in:
2302:22
2702:A2 ;
2B02:14
2F02:88 ;
3302:8
3702:8
3B02:8
![Screenshot 5](pics/hgrfont_05.png?raw=true)
We actually _also_ need to moving the left-edge pixel over by 1 so it appears in the correct location when shifted:
2304:22
2704:92 ;
2B04:14
2F04:8C ;
3304:8
3704:8
3B04:8
Ah-ha! We've got "smooth" `Y`.
![Screenshot 6](pics/hgrfont_06.png?raw=true)
**Note**: The emulators `Virtual ][` and `Apple2js` are *broken* emulators. They do **not** emulate the half-pixel shift of real hardware at all. This is another reason we won't worry about it for now. **Note**: The emulators `Virtual ][` and `Apple2js` are *broken* emulators. They do **not** emulate the half-pixel shift of real hardware at all. This is another reason we won't worry about it for now.
We're going to ignore the half-pixel shift since it is easy to touch up the font data later if we wish: We're going to ignore the half-pixel shift since it is easy to touch up the font data later if we wish.
At the beginning we said to view the HGR screen in monochrome; Notice how the extra colors make the Hi-Res text much harder to read. If you are running on real hardware the Apple Color Composite Monitor had a push-button on the front to toggle the screen between color and monochrome. Now we know why!
![Screenshot 7](pics/hgrfont_07.png?raw=true)
## Font Data ## Font Data

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