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/*
Copyright (C) 2015 Aaron Suen <warr1024@gmail.com>
This program is free software; you can redistribute it and/or modify
it under the terms of the GNU Lesser General Public License as published by
the Free Software Foundation; either version 2.1 of the License, or
(at your option) any later version.
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU Lesser General Public License for more details.
You should have received a copy of the GNU Lesser General Public License along
with this program; if not, write to the Free Software Foundation, Inc.,
51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
*/
#include "imagefilters.h"
#include "util/numeric.h"
#include <cmath>
/* Fill in RGB values for transparent pixels, to correct for odd colors
* appearing at borders when blending. This is because many PNG optimizers
* like to discard RGB values of transparent pixels, but when blending then
* with non-transparent neighbors, their RGB values will shpw up nonetheless.
*
* This function modifies the original image in-place.
*
* Parameter "threshold" is the alpha level below which pixels are considered
* transparent. Should be 127 for 3d where alpha is threshold, but 0 for
* 2d where alpha is blended.
*/
void imageCleanTransparent(video::IImage *src, u32 threshold)
{
core::dimension2d<u32> dim = src->getDimension();
// Walk each pixel looking for fully transparent ones.
// Note: loop y around x for better cache locality.
for (u32 ctry = 0; ctry < dim.Height; ctry++)
for (u32 ctrx = 0; ctrx < dim.Width; ctrx++) {
// Ignore opaque pixels.
irr::video::SColor c = src->getPixel(ctrx, ctry);
if (c.getAlpha() > threshold)
continue;
// Sample size and total weighted r, g, b values.
u32 ss = 0, sr = 0, sg = 0, sb = 0;
// Walk each neighbor pixel (clipped to image bounds).
for (u32 sy = (ctry < 1) ? 0 : (ctry - 1);
sy <= (ctry + 1) && sy < dim.Height; sy++)
for (u32 sx = (ctrx < 1) ? 0 : (ctrx - 1);
sx <= (ctrx + 1) && sx < dim.Width; sx++) {
// Ignore transparent pixels.
irr::video::SColor d = src->getPixel(sx, sy);
if (d.getAlpha() <= threshold)
continue;
// Add RGB values weighted by alpha.
u32 a = d.getAlpha();
ss += a;
sr += a * d.getRed();
sg += a * d.getGreen();
sb += a * d.getBlue();
}
// If we found any neighbor RGB data, set pixel to average
// weighted by alpha.
if (ss > 0) {
c.setRed(sr / ss);
c.setGreen(sg / ss);
c.setBlue(sb / ss);
src->setPixel(ctrx, ctry, c);
}
}
}
/* Scale a region of an image into another image, using nearest-neighbor with
* anti-aliasing; treat pixels as crisp rectangles, but blend them at boundaries
* to prevent non-integer scaling ratio artifacts. Note that this may cause
* some blending at the edges where pixels don't line up perfectly, but this
* filter is designed to produce the most accurate results for both upscaling
* and downscaling.
*/
void imageScaleNNAA(video::IImage *src, const core::rect<s32> &srcrect, video::IImage *dest)
{
double sx, sy, minsx, maxsx, minsy, maxsy, area, ra, ga, ba, aa, pw, ph, pa;
u32 dy, dx;
video::SColor pxl;
// Cache rectsngle boundaries.
double sox = srcrect.UpperLeftCorner.X * 1.0;
double soy = srcrect.UpperLeftCorner.Y * 1.0;
double sw = srcrect.getWidth() * 1.0;
double sh = srcrect.getHeight() * 1.0;
// Walk each destination image pixel.
// Note: loop y around x for better cache locality.
core::dimension2d<u32> dim = dest->getDimension();
for (dy = 0; dy < dim.Height; dy++)
for (dx = 0; dx < dim.Width; dx++) {
// Calculate floating-point source rectangle bounds.
// Do some basic clipping, and for mirrored/flipped rects,
// make sure min/max are in the right order.
minsx = sox + (dx * sw / dim.Width);
minsx = rangelim(minsx, 0, sw);
maxsx = minsx + sw / dim.Width;
maxsx = rangelim(maxsx, 0, sw);
if (minsx > maxsx)
SWAP(double, minsx, maxsx);
minsy = soy + (dy * sh / dim.Height);
minsy = rangelim(minsy, 0, sh);
maxsy = minsy + sh / dim.Height;
maxsy = rangelim(maxsy, 0, sh);
if (minsy > maxsy)
SWAP(double, minsy, maxsy);
// Total area, and integral of r, g, b values over that area,
// initialized to zero, to be summed up in next loops.
area = 0;
ra = 0;
ga = 0;
ba = 0;
aa = 0;
// Loop over the integral pixel positions described by those bounds.
for (sy = floor(minsy); sy < maxsy; sy++)
for (sx = floor(minsx); sx < maxsx; sx++) {
// Calculate width, height, then area of dest pixel
// that's covered by this source pixel.
pw = 1;
if (minsx > sx)
pw += sx - minsx;
if (maxsx < (sx + 1))
pw += maxsx - sx - 1;
ph = 1;
if (minsy > sy)
ph += sy - minsy;
if (maxsy < (sy + 1))
ph += maxsy - sy - 1;
pa = pw * ph;
// Get source pixel and add it to totals, weighted
// by covered area and alpha.
pxl = src->getPixel((u32)sx, (u32)sy);
area += pa;
ra += pa * pxl.getRed();
ga += pa * pxl.getGreen();
ba += pa * pxl.getBlue();
aa += pa * pxl.getAlpha();
}
// Set the destination image pixel to the average color.
if (area > 0) {
pxl.setRed(ra / area + 0.5);
pxl.setGreen(ga / area + 0.5);
pxl.setBlue(ba / area + 0.5);
pxl.setAlpha(aa / area + 0.5);
} else {
pxl.setRed(0);
pxl.setGreen(0);
pxl.setBlue(0);
pxl.setAlpha(0);
}
dest->setPixel(dx, dy, pxl);
}
}
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