must be rounded to integer values for the number of rows
and of columns on the screen, which is done by integer
functions u and v (equations (4)):
f( X ) = N * b/a * x and g< y ) = N * y
u = L f( X ) J and v = L g (y) J (4)
L J - integer.
To explain this theoretical consideration in Table 8, we
have given a presentation of the translation of scan pixels
into screen pixels on a 15” screen with tension mask.
Pixels are selected at random, and in this concrete case
they have been selected from the 72 nd and 73 rd row of the
pixmap (see; part a) of the figure 9). Calculations have
been carried out for one case of image decrease by a
non-round number (zoom out 67%) and for two cases of
image increase (zoom in 170% and 800%). With image
decrease, a selection is made so that - thanks to the
effect of rounding up the numbers to get integer numbers
for rows and columns - it is possible to show only a part
of the original scan pixels on the screen.
a) b)
Figure 9: Translation of scan pixels from a pixmap a) into
the coordinate system of the screen with shadow mask b).
On the basis of the zoom factor N, the theoretical width of
the screen pixel a, the theoretical height of the screen
pixel p, the width of the column a and the height of the
half-row b, the following translation coefficients s x and s y
of the scaling matrix Ms are defined for screens with a
shadow mask (equations (5)):
s x = N * a / a and s y = N * p / b (5)
Pixmap
15" screen with tension mask
640x480 (axb = 0,25x0,44; b/a=1,76)
N = 0,67
(67%- decrease)
N = 1,7
(170%-increase)
N = 8
(800%-increase)
x
V
f(x)
g(y)
u
v
f(x)
g(y)
u
v
f(x)
g(y)
u
V
P 51,73
2x0=
3x2=
14x8=
0 Pixel
6 Pixel
112 Pixel
A
50
72
58,96
48,24
58
48
149,6
122,4
149
122
704
576
704
576
B
51
73
60,14
48,91
60
48
152,59
124,1
152
124
718,08
584
718
584
P 52,73
1x0=
3x2=
14x8=
0 Pixel
6 Pixel
112 Pixel
A
51
72
60,14
48,24
60
48
152,59
122,4
152
122
718,08
576
718
576
B
52
73
61,32
48,91
61
48
155,58
124,1
155
124
732,16
584
732
584
P 53,73
1x0=
3x2=
14x8=
0 Pixel
6 Pixel
112 Pixel
A
52
72
61,32
48,24
61
48
155,58
122,4
155
122
732,16
576
732
576
B
53
73
62,50
48,91
62
48
158,58
124,1
158
124
746,24
584
746
584
P51.74
2x1 =
3x1 =
14x8=
2 Pixel
3 Pixel
112 Pixel
A
50
73
58,96
48,91
58
48
149,6
124,1
149
124
704
584
704
584
B
51
74
60,14
49,58
60
49
152,59
125,8
152
125
718,08
592
718
592
P5274
1x1 =
3x1 =
14x8=
1 Pixel
3 Pixel
112 Pixel
A
51
73
60,14
48,91
60
48
152,59
124,1
152
124
718,08
584
718
584
B
52
74
61,32
49,58
61
49
155,58
125,8
155
125
732,16
592
732
592
P 53,74
1x1 =
3x1 =
14x8=
1 Pixel
3 Pixel
112 Pixel
A
52
73
61,32
48,91
61
48
155,58
124,1
155
124
732,16
584
732
584
B
53
74
62,50
49,58
62
49
158,58
125,8
158
125
746,24
592
746
592
Table 8: Presentation of the translation of pixmap => screen at a decrease (zoom out 67%)
and increase (zoom in 170% and 800%) on the example of a 15” screen with tension mask.
Since the pixels in a screen with shadow mask are of a
triangular, the so-called “delta” shape, and the number
and intervals of apertures in the shadow mask are fixed,
there are some differences in the translation coefficients
s x and s y of the scaling matrix Ms. The translation of the
translation of the pixmap into the coordinate system of a
17” screen with shadow mask is presented in figure 9. For
calculation purposes, a quasi “half-row” coordinate system
has been formed for rows and columns, and this system is
then laid over the sample of screen pixels. To show this
more clearly, only the apertures of the shadow mask and
not whole screen pixels are shown in the figure.
Translation functions f( X ) and g< y ) for screens with shadow
mask are defined on the analo-gy of the translation in the
screens with ten-sion mask (equations (6)):
f(x) = N*a/a*x and g( y ) = N*p/b*y
u = L f (X ) J and v = L g(y) J (6)
L J - integer.
The explanation of this theoretical pre-sentation is given in
table 10, and it also corresponds with the presentation in
figure 9.
