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#define __NR_PIXBLOCK_SCALER_CPP__
/*
* Functions for blitting pixblocks using scaling
*
* Author:
* Niko Kiirala <niko@kiirala.com>
*
* Copyright (C) 2006 Niko Kiirala
*
* Released under GNU GPL, read the file 'COPYING' for more information
*/
#include <glib.h>
#include <cmath>
using std::floor;
#include "libnr/nr-pixblock.h"
namespace NR {
struct RGBA {
int r, g, b, a;
};
/** Calculates cubically interpolated value of the four given pixel values.
* The pixel values should be from four vertically adjacent pixels.
* If we are calculating a pixel, whose y-coordinate in source image is
* i, these pixel values a, b, c and d should come from lines
* floor(i) - 1, floor(i), floor(i) + 1, floor(i) + 2, respectively.
* Parameter len should be set to i.
* Returns the interpolated value in fixed point format with 8 bit
* decimal part. (24.8 assuming 32-bit int)
*/
__attribute__ ((const))
inline int sampley(unsigned const char a, unsigned const char b,
unsigned const char c, unsigned const char d,
const double len)
{
double lenf = len - floor(len);
int sum = 0;
sum += (int)((((-1.0 / 3.0) * lenf + 4.0 / 5.0) * lenf - 7.0 / 15.0)
* lenf * 256 * a);
sum += (int)((((lenf - 9.0 / 5.0) * lenf - 1.0 / 5.0) * lenf + 1.0)
* 256 * b);
sum += (int)(((((1 - lenf) - 9.0 / 5.0) * (1 - lenf) - 1.0 / 5.0)
* (1 - lenf) + 1.0) * 256 * c);
sum += (int)((((-1.0 / 3.0) * (1 - lenf) + 4.0 / 5.0) * (1 - lenf)
- 7.0 / 15.0) * (1 - lenf) * 256 * d);
return sum;
}
/** Calculates cubically interpolated value of the four given pixel values.
* The pixel values should be interpolated values from sampley, from four
* horizontally adjacent vertical lines. The parameters a, b, c and d
* should be in fixed point format with 8-bit decimal part.
* If we are calculating a pixel, whose x-coordinate in source image is
* i, these vertical lines from where a, b, c and d are calculated, should be
* floor(i) - 1, floor(i), floor(i) + 1, floor(i) + 2, respectively.
* Parameter len should be set to i.
* Returns the interpolated value in 8-bit format, ready to be written
* to output buffer.
*/
inline unsigned char samplex(const int a, const int b, const int c, const int d, const double len) {
double lenf = len - floor(len);
int sum = 0;
sum += (int)(a * (((-1.0 / 3.0) * lenf + 4.0 / 5.0) * lenf - 7.0 / 15.0) * lenf);
sum += (int)(b * (((lenf - 9.0 / 5.0) * lenf - 1.0 / 5.0) * lenf + 1.0));
sum += (int)(c * ((((1 - lenf) - 9.0 / 5.0) * (1 - lenf) - 1.0 / 5.0) * (1 - lenf) + 1.0));
sum += (int)(d * (((-1.0 / 3.0) * (1 - lenf) + 4.0 / 5.0) * (1 - lenf) - 7.0 / 15.0) * (1 - lenf));
if (sum < 0) sum = 0;
if (sum >= 256*256) sum = 255 * 256;
return (unsigned char)(sum / 256);
}
/**
* Sanity check function for indexing pixblocks.
* Catches reading and writing outside the pixblock area.
* When enabled, decreases filter rendering speed massively.
*/
inline void _check_index(NRPixBlock const * const pb, int const location, int const line)
{
if(false) {
int max_loc = pb->rs * (pb->area.y1 - pb->area.y0);
if (location < 0 || (location + 4) > max_loc)
g_warning("Location %d out of bounds (0 ... %d) at line %d", location, max_loc, line);
}
}
void scale_bicubic(NRPixBlock *to, NRPixBlock *from)
{
if (NR_PIXBLOCK_BPP(from) != 4 || NR_PIXBLOCK_BPP(to) != 4) {
g_warning("A non-32-bpp image passed to scale_bicubic: scaling aborted.");
return;
}
// 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;
// from_step: when advancing one pixel in destination image,
// how much we should advance in source image
double from_stepx = (double)from_width / (double)to_width;
double from_stepy = (double)from_height / (double)to_height;
// Loop through every pixel of destination image, a line at a time
for (int to_y = 0 ; to_y < to_height ; to_y++) {
double from_y = to_y * from_stepy + from_stepy / 2;
// Pre-calculate beginning of the four horizontal lines, from
// which we should read
int from_line[4];
for (int i = 0 ; i < 4 ; i++) {
if ((int)floor(from_y) + i - 1 >= 0) {
if ((int)floor(from_y) + i - 1 < from_height) {
from_line[i] = ((int)floor(from_y) + i - 1) * from->rs;
} else {
from_line[i] = (from_height - 1) * from->rs;
}
} else {
from_line[i] = 0;
}
}
// Loop through this horizontal line in destination image
// For every pixel, calculate the color of pixel with
// bicubic interpolation and set the pixel value in destination image
for (int to_x = 0 ; to_x < to_width ; to_x++) {
double from_x = to_x * from_stepx + from_stepx / 2;
RGBA line[4];
for (int i = 0 ; i < 4 ; i++) {
int k = (int)floor(from_x) + i - 1;
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 = sampley(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 = sampley(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 = sampley(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 = sampley(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 = samplex(line[0].r, line[1].r, line[2].r, line[3].r,
from_x);
result.g = samplex(line[0].g, line[1].g, line[2].g, line[3].g,
from_x);
result.b = samplex(line[0].b, line[1].b, line[2].b, line[3].b,
from_x);
result.a = samplex(line[0].a, line[1].a, line[2].a, line[3].a,
from_x);
_check_index(to, to_y * to->rs + to_x * 4, __LINE__);
NR_PIXBLOCK_PX(to)[to_y * to->rs + to_x * 4] = result.r;
NR_PIXBLOCK_PX(to)[to_y * to->rs + to_x * 4 + 1] = result.g;
NR_PIXBLOCK_PX(to)[to_y * to->rs + to_x * 4 + 2] = result.b;
NR_PIXBLOCK_PX(to)[to_y * to->rs + to_x * 4 + 3] = result.a;
}
}
}
} /* namespace NR */
/*
Local Variables:
mode:c++
c-file-style:"stroustrup"
c-file-offsets:((innamespace . 0)(inline-open . 0)(case-label . +))
indent-tabs-mode:nil
fill-column:99
End:
*/
// vim: filetype=cpp:expandtab:shiftwidth=4:tabstop=8:softtabstop=4:encoding=utf-8:textwidth=99 :
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