Michael Hanke schrieb:
>Ok. Now that you have said "A" I would ask that you should also say "B": Would
>it be possible to get a copy of your filter for experimenting, ideally with
>adescription of the theory behind it since you said it's non-standard.
>
OK, here we go...
This is a much simplified and a lot faster variant of that scaler. It
took me some minutes to make it useful and understandable... (I hope)...
void
upscale (uint8_t * dst, uint8_t * src, int w, int h)
{
// triangulation scaler
// this scaler works by analysing the correlations between neighboring
pixels
// it is a rather simple "super-resolution-approach" but as TV is
lowpassfiltered
// in front of transmission we can't recover resolution with a
multi-image approach
// so if upscaling is needed at all, we try to do it visually correct...
//
// the results are quite similar to what modern plasma-screens do with
SD-signals
int x, y;
int dx, dy;
int m;
int a, b, c, d;
int ae, be, ce, de, me;
for (y = 0; y <= h; y++)
for (x = 0; x <= w; x++)
{
*(dst + (x * 2) + (y * 2) * (w * 2)) = *(src + x + y * w);
}
w *= 2;
h *= 2;
for (y = 1; y <= h; y += 2)
for (x = 1; x <= w; x += 2)
{
// fill in the four neighbor-pixels
a = *(dst + (x - 1) + (y - 1) * w);
b = *(dst + (x + 1) + (y - 1) * w);
c = *(dst + (x - 1) + (y + 1) * w);
d = *(dst + (x + 1) + (y + 1) * w);
// calculate the mean of the neighbors
m = (a + b + c + d) / 4;
// calculate the error for every neighbor-pixel
ae = (m - a) * (m - a);
be = (m - b) * (m - b);
ce = (m - c) * (m - c);
de = (m - d) * (m - d);
// find the maximum error-value
me = ae;
me = (me < be) ? be : me;
me = (me < ce) ? ce : me;
me = (me < de) ? de : me;
// generate mixing coefficients
ae = me - ae;
be = me - be;
ce = me - ce;
de = me - de;
me = ae + be + ce + de;
if (me != 0)
m = (a * ae + b * be + c * ce + d * de) / me;
*(dst + x + y * w) = m;
}
for (y = 0; y <= h; y += 2)
for (x = 1; x <= w; x += 2)
{
// fill in the four neighbor-pixels
a = *(dst + (x - 1) + y * w);
b = *(dst + (x + 1) + y * w);
c = *(dst + x + (y - 1) * w);
d = *(dst + x + (y + 1) * w);
// calculate the mean of the neighbors
m = (a + b + c + d) / 4;
// calculate the error for every neighbor-pixel
ae = (m - a) * (m - a);
be = (m - b) * (m - b);
ce = (m - c) * (m - c);
de = (m - d) * (m - d);
// find the maximum error-value
me = ae;
me = (me < be) ? be : me;
me = (me < ce) ? ce : me;
me = (me < de) ? de : me;
// generate mixing coefficients
ae = me - ae;
be = me - be;
ce = me - ce;
de = me - de;
me = ae + be + ce + de;
if (me != 0)
m = (a * ae + b * be + c * ce + d * de) / me;
*(dst + x + y * w) = m;
}
for (y = 1; y <= h; y += 2)
for (x = 0; x <= w; x += 2)
{
// fill in the four neighbor-pixels
a = *(dst + (x - 1) + y * w);
b = *(dst + (x + 1) + y * w);
c = *(dst + x + (y - 1) * w);
d = *(dst + x + (y + 1) * w);
// calculate the mean of the neighbors
m = (a + b + c + d) / 4;
// calculate the error for every neighbor-pixel
ae = (m - a) * (m - a);
be = (m - b) * (m - b);
ce = (m - c) * (m - c);
de = (m - d) * (m - d);
// find the maximum error-value
me = ae;
me = (me < be) ? be : me;
me = (me < ce) ? ce : me;
me = (me < de) ? de : me;
// generate mixing coefficients
ae = me - ae;
be = me - be;
ce = me - ce;
de = me - de;
me = ae + be + ce + de;
if (me != 0)
m = (a * ae + b * be + c * ce + d * de) / me;
*(dst + x + y * w) = m;
}
// only very little lowpass-filtering (sometimes looks better
sometimes not...)...
#if 0
for (y = 0; y <= h; y++)
for (x = 0; x <= w; x++)
{
a = *(dst + (x - 1) + (y - 1) * w);
b = *(dst + (x + 1) + (y - 1) * w);
c = *(dst + (x - 1) + (y + 1) * w);
d = *(dst + (x + 1) + (y + 1) * w);
m = (a + b + c + d) / 4;
m += *(dst + x + y * w) * 3;
m /= 4;
*(dst + x + y * w) = m;
}
#endif
}
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