void transform_bicubic(NRPixBlock *to, NRPixBlock *from, Geom::Matrix const &trans)
{
if (NR_PIXBLOCK_BPP(from) != 4 || NR_PIXBLOCK_BPP(to) != 4) {
g_warning("A non-32-bpp image passed to transform_bicubic: scaling aborted.");
return;
}
bool free_from_on_exit = false;
if (from->mode != to->mode){
NRPixBlock *o_from = from;
from = new NRPixBlock;
nr_pixblock_setup_fast(from, to->mode, o_from->area.x0, o_from->area.y0, o_from->area.x1, o_from->area.y1, false);
nr_blit_pixblock_pixblock(from, o_from);
free_from_on_exit = true;
}
if (from->mode != NR_PIXBLOCK_MODE_R8G8B8A8P) {
// TODO: Fix this... (The problem is that for interpolation non-premultiplied colors should be premultiplied...)
g_warning("transform_bicubic does not properly support non-premultiplied images");
}
// Precalculate sizes of source and destination pixblocks
int from_width = from->area.x1 - from->area.x0;
int from_height = from->area.y1 - from->area.y0;
int to_width = to->area.x1 - to->area.x0;
int to_height = to->area.y1 - to->area.y0;
Geom::Matrix itrans = trans.inverse();
// Loop through every pixel of destination image, a line at a time
for (int to_y = 0 ; to_y < to_height ; to_y++) {
for (int to_x = 0 ; to_x < to_width ; to_x++) {
double from_x = itrans[0] * (to_x + 0.5 + to->area.x0)
+ itrans[2] * (to_y + 0.5 + to->area.y0)
+ itrans[4] - from->area.x0;
double from_y = itrans[1] * (to_x + 0.5 + to->area.x0)
+ itrans[3] * (to_y + 0.5 + to->area.y0)
+ itrans[5] - from->area.y0;
if (from_x < 0 || from_x >= from_width ||
from_y < 0 || from_y >= from_height) {
continue;
}
RGBA line[4];
int from_line[4];
for (int i = 0 ; i < 4 ; i++) {
int fy_line = (int)round(from_y) + i - 2;
if (fy_line >= 0) {
if (fy_line < from_height) {
from_line[i] = fy_line * from->rs;
} else {
from_line[i] = (from_height - 1) * from->rs;
}
} else {
from_line[i] = 0;
}
}
for (int i = 0 ; i < 4 ; i++) {
int k = (int)round(from_x) + i - 2;
if (k < 0) k = 0;
if (k >= from_width) k = from_width - 1;
k *= 4;
_check_index(from, from_line[0] + k, __LINE__);
_check_index(from, from_line[1] + k, __LINE__);
_check_index(from, from_line[2] + k, __LINE__);
_check_index(from, from_line[3] + k, __LINE__);
line[i].r = sample(NR_PIXBLOCK_PX(from)[from_line[0] + k],
NR_PIXBLOCK_PX(from)[from_line[1] + k],
NR_PIXBLOCK_PX(from)[from_line[2] + k],
NR_PIXBLOCK_PX(from)[from_line[3] + k],
from_y);
line[i].g = sample(NR_PIXBLOCK_PX(from)[from_line[0] + k + 1],
NR_PIXBLOCK_PX(from)[from_line[1] + k + 1],
NR_PIXBLOCK_PX(from)[from_line[2] + k + 1],
NR_PIXBLOCK_PX(from)[from_line[3] + k + 1],
from_y);
line[i].b = sample(NR_PIXBLOCK_PX(from)[from_line[0] + k + 2],
NR_PIXBLOCK_PX(from)[from_line[1] + k + 2],
NR_PIXBLOCK_PX(from)[from_line[2] + k + 2],
NR_PIXBLOCK_PX(from)[from_line[3] + k + 2],
from_y);
line[i].a = sample(NR_PIXBLOCK_PX(from)[from_line[0] + k + 3],
NR_PIXBLOCK_PX(from)[from_line[1] + k + 3],
NR_PIXBLOCK_PX(from)[from_line[2] + k + 3],
NR_PIXBLOCK_PX(from)[from_line[3] + k + 3],
from_y);
}
RGBA result;
result.r = round(sample(line[0].r, line[1].r, line[2].r, line[3].r,
from_x));
result.g = round(sample(line[0].g, line[1].g, line[2].g, line[3].g,
from_x));
result.b = round(sample(line[0].b, line[1].b, line[2].b, line[3].b,
from_x));
result.a = round(sample(line[0].a, line[1].a, line[2].a, line[3].a,
from_x));
using Inkscape::Filters::clamp;
using Inkscape::Filters::clamp_alpha;
_check_index(to, to_y * to->rs + to_x * 4, __LINE__);
if (to->mode == NR_PIXBLOCK_MODE_R8G8B8A8P) {
/* Make sure, none of the RGB channels exceeds 100% intensity
* in premultiplied output */
int const alpha = clamp((int)result.a);
NR_PIXBLOCK_PX(to)[to_y * to->rs + to_x * 4] =
clamp_alpha((int)result.r, alpha);
NR_PIXBLOCK_PX(to)[to_y * to->rs + to_x * 4 + 1] =
clamp_alpha((int)result.g, alpha);
NR_PIXBLOCK_PX(to)[to_y * to->rs + to_x * 4 + 2] =
clamp_alpha((int)result.b, alpha);
NR_PIXBLOCK_PX(to)[to_y * to->rs + to_x * 4 + 3] = alpha;
} else {
/* Clamp the output to unsigned char range */
NR_PIXBLOCK_PX(to)[to_y * to->rs + to_x * 4]
= clamp((int)result.r);
NR_PIXBLOCK_PX(to)[to_y * to->rs + to_x * 4 + 1]
= clamp((int)result.g);
NR_PIXBLOCK_PX(to)[to_y * to->rs + to_x * 4 + 2]
= clamp((int)result.b);
NR_PIXBLOCK_PX(to)[to_y * to->rs + to_x * 4 + 3]
= clamp((int)result.a);
}
}
}
if (free_from_on_exit) {
nr_pixblock_release(from);
delete from;
}
}
