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index 3b8461383d4eacf1ff4957e3ca2e59b44028175a..c5acaace0b3e5f4f033accc3ac7457715e031dcd 100644 (file)
#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;
int r, g, b, a;
};
-inline int sampley(unsigned const char a, unsigned const char b, unsigned const char c, unsigned const char d, const double len) {
+/** 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)
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)(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 > 255*256) sum = 255 * 256;
+ if (sum >= 256*256) sum = 255 * 256;
return (unsigned char)(sum / 256);
}
@@ -45,25 +80,36 @@ inline unsigned char samplex(const int a, const int b, const int c, const int d,
*/
inline void _check_index(NRPixBlock const * const pb, int const location, int const line)
{
- if(true) {
+ if(false) {
int max_loc = pb->rs * (pb->area.y1 - pb->area.y0);
- if (location < 0 || (location + 4) >= max_loc)
+ 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) {
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];