#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 :