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Improve image_scale_tpl() performance using an iterator for source image

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This commit is contained in:
David Capello 2016-03-22 18:23:03 -03:00
parent 14262c270c
commit ce02a31c01
1 changed files with 15 additions and 4 deletions
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19
src/doc/algorithm/rotate.cpp
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@ -47,21 +47,32 @@ static void image_scale_tpl(
{
LockImageBits<ImageTraits> dst_bits(dst, gfx::Rect(dst_x, dst_y, dst_w, dst_h));
typename LockImageBits<ImageTraits>::iterator dst_it = dst_bits.begin();
fixed x;
fixed x, first_x = itofix(src_x);
fixed y = itofix(src_y);
fixed dx = fixdiv(itofix(src_w-1), itofix(dst_w-1));
fixed dy = fixdiv(itofix(src_h-1), itofix(dst_h-1));
int old_x, new_x;
for (int v=0; v<dst_h; ++v) {
x = itofix(src_x);
old_x = fixtoi(x = first_x);
const LockImageBits<ImageTraits> src_bits(src, gfx::Rect(src_x, fixtoi(y), src_w, 1));
auto src_it = src_bits.begin();
for (int u=0; u<dst_w; ++u) {
ASSERT(dst_it != dst_bits.end());
color_t src_color = get_pixel_fast<ImageTraits>(src, fixtoi(x), fixtoi(y));
*dst_it = blend(*dst_it, src_color);
*dst_it = blend(*dst_it, *src_it);
++dst_it;
x = fixadd(x, dx);
new_x = fixtoi(x);
if (old_x != new_x) {
src_it += (new_x - old_x);
old_x = new_x;
}
}
y = fixadd(y, dy);
}
}