ultimatepp/uppsrc/Draw/RescaleFilter.cpp

#include "Draw.h"

namespace Upp {

#define LDUMP(x) // DUMP(x)

static const int *sGetKernel(double (*kfn)(double x), int a, int shift)
{
	INTERLOCKED {
		static VectorMap<Tuple3<uintptr_t, int, int>, Buffer<int> > kache;
		Tuple3<uintptr_t, int, int> key = MakeTuple((uintptr_t)kfn, a, shift);
		Buffer<int> *k = kache.FindPtr(key);
		if(k)
			return *k;
		Buffer<int>& ktab = kache.GetAdd(key);
		ktab.Alloc(((2 * a) << shift) + 1);
		for(int i = 0; i < ((2 * a) << shift) + 1; i++)
			ktab[i] = int((1 << shift) * (*kfn)((double)i / (1 << shift) - a));
		return ktab;
	}
	return NULL;
}

force_inline
int sGetk(const int *kernel, int x, int a, int shift)
{
	x += a << shift;
	ASSERT(x >= 0 && x < ((2 * a) << shift) + 1);
	x = minmax(x, 0, (2 * a) << shift);
	return kernel[x];
}

static int sGeta(int a, int src, int tgt, int& shift)
{
	int n = min(max(src / tgt, 1) * a, 31);
	shift = 8 - n / 8;
	return n;
}

Image RescaleFilter(const Image& img, Size sz, const Rect& sr,
                    double (*kfn)(double x), int a,
                    Gate<int, int> progress)
{
	ASSERT(Rect(img.GetSize()).Contains(sr));
	Size isz = sr.GetSize();
	
	if(isz.cx <= 0 || isz.cy <= 0 || sz.cx <= 0 || sz.cy <= 0)
		return Image();

	int shiftx, shifty;
	int ax = sGeta(a, isz.cx, sz.cx, shiftx);
	int ay = sGeta(a, isz.cy, sz.cy, shifty);

	int shift = min(shiftx, shifty);
	
	const int *kernel = sGetKernel(kfn, a, shift);

	Buffer<int> px(sz.cx * 2 * ax * 2 * ay * 2);
	int *xd = px;
	Size cr = (Size(1 << shift, 1 << shift) - (isz << shift) / sz) >> 1;
	for(int x = 0; x < sz.cx; x++) {
		int dx = ((x * isz.cx) << shift) / sz.cx - cr.cx;
		int sx = dx >> shift;
		dx -= sx << shift;
		if(dx < 0)
			dx = 0;
		for(int yy = -ay + 1; yy <= ay; yy++)
			for(int xx = -ax + 1; xx <= ax; xx++) {
				*xd++ = minmax(sx + xx, 0, isz.cx - 1) + sr.left;
				*xd++ = sGetk(kernel, ((xx << shift) - dx) * a / ax, a, shift);
			}
	}

	ImageBuffer ib(sz);
	RGBA *t = ~ib;
	for(int y = 0; y < sz.cy; y++) {
		if(progress(y, sz.cy))
			break;
		int dy = ((y * isz.cy) << shift) / sz.cy - cr.cy;
		int sy = dy >> shift;
		dy -= sy << shift;
		if(dy < 0)
			dy = 0;
		xd = ~px;
		Buffer<int> py(2 * ay * 2);
		int *yd = py;
		for(int yy = -ay + 1; yy <= ay; yy++) {
			*yd++ = sGetk(kernel, ((yy << shift) - dy) * a / ay, a, shift);
			*yd++ = minmax(sy + yy, 0, isz.cy - 1) + sr.top;
		}
		for(int x = 0; x < sz.cx; x++) {
			int red   = 0;
			int green = 0;
			int blue  = 0;
			int alpha = 0;
			int w = 0;
			yd = py;
			int hasalpha = 0;
			for(int yy = 2 * ay; yy-- > 0;) {
				int ky = *yd++;
				const RGBA *l = img[*yd++];
				for(int xx = 2 * ax; xx-- > 0;) {
					const RGBA& s = l[*xd++];
					int weight = ky * *xd++;
					red   += weight * s.r;
					green += weight * s.g;
					blue  += weight * s.b;
					alpha += weight * s.a;
					hasalpha |= s.a - 255;
					w += weight;
				}
			}
			if(w)
				if(hasalpha) {
					t->a = alpha = Saturate255(alpha / w);
					t->r = clamp(red / w, 0, alpha);
					t->g = clamp(green / w, 0, alpha);
					t->b = clamp(blue / w, 0, alpha);
				}
				else {
					t->a = 255;
					t->r = Saturate255(red / w);
					t->g = Saturate255(green / w);
					t->b = Saturate255(blue / w);
				}
			else
				t->a = t->r = t->g = t->b = 0;
			t++;
		}
	}
	ib.SetResolution(img.GetResolution());
	return ib;
}

Image RescaleFilter(const Image& img, Size sz,
                    double (*kfn)(double x), int a,
                    Gate<int, int> progress)
{
	return RescaleFilter(img, sz, img.GetSize(), kfn, a, progress);
}

Image RescaleFilter(const Image& img, int cx, int cy,
                    double (*kfn)(double x), int a,
                    Gate<int, int> progress)
{
	return RescaleFilter(img, Size(cx, cy), img.GetSize(), kfn, a, progress);
}

static double sNearest(double x)
{
	return (double)(x >= -0.5 && x <= 0.5);
}


static double sBiCubic_(double x, double B, double C)
{
	x = fabs(x);
	double x2 = x * x;
	double x3 = x * x * x;
	return
		1 / 6.0 * (x < 1 ? (12 - 9*B - 6*C) * x3 + (-18 + 12*B + 6*C) * x2 + (6 - 2*B) :
		           x < 2 ? (-B - 6*C) * x3 + (6*B + 30*C) * x2 + (-12*B - 48*C) *x + (8*B + 24*C) :
	               0);
}

static double sBspline(double x)
{
	return sBiCubic_(x, 1, 0);
}

static double sMitchell(double x)
{
	return sBiCubic_(x, 1 / 3.0, 1 / 3.0);
}

static double sCatmullRom(double x)
{
	return sBiCubic_(x, 0, 1 / 2);
}

static double sLinear(double x)
{
	x = fabs(x);
	if(x > 1)
		return 0;
	return 1 - fabs(x);
}

static double sLanczos(double x, int a)
{
	x = fabs(x);
	if(x < 1e-200)
		return 1;
	if(x >= a)
		return 0;
	return a * sin(M_PI * x) * sin(M_PI * x / a) / (M_PI * M_PI * x * x);
}

static double sLanczos2(double x)
{
	return sLanczos(x, 2);
}

static double sLanczos3(double x)
{
	return sLanczos(x, 3);
}

static double sLanczos4(double x)
{
	return sLanczos(x, 4);
}

static double sLanczos5(double x)
{
	return sLanczos(x, 5);
}

static double sCostello(double x)
{
	x = fabs(x);
	return x < 0.5 ? 0.75 - x * x :
	       x < 1.5 ? 0.5 * (x - 1.5) * (x - 1.5) :
	       0;
}

Image RescaleFilter(const Image& img, Size sz, const Rect& sr, int filter, Gate<int, int> progress)
{
	if(IsNull(filter))
		return Rescale(img, sz, sr);
	static Tuple2<double (*)(double), int> tab[] = {
		{ sNearest, 1 },
		{ sLinear, 1 },
		{ sBspline, 2 },
		{ sCostello, 2 },
		{ sMitchell, 2 },
		{ sCatmullRom, 2 },
		{ sLanczos2, 2 },
		{ sLanczos3, 3 },
		{ sLanczos4, 4 },
		{ sLanczos5, 5 },
	};
	ASSERT(filter >= FILTER_NEAREST && filter <= FILTER_LANCZOS5);
	return RescaleFilter(img, sz, sr, tab[filter].a, tab[filter].b, progress);
}

Image RescaleFilter(const Image& img, Size sz, int filter, Gate<int, int> progress)
{
	return RescaleFilter(img, sz, img.GetSize(), filter, progress);
}

Image RescaleFilter(const Image& img, int cx, int cy, int filter, Gate<int, int> progress)
{
	return RescaleFilter(img, Size(cx, cy), filter, progress);
}

}