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Using simple bilinear interpolation when scaling stamps up.

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This commit is contained in:
William Kendrick 2006-11-02 09:05:03 +00:00
parent b765c86e50
commit 666e011b5c
3 changed files with 135 additions and 7 deletions
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6
docs/AUTHORS.txt
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@ -7,7 +7,7 @@ bill@newbreedsoftware.com
http://www.tuxpaint.org/
June 17, 2002 - October 18, 2006
June 17, 2002 - November 1, 2006
$Id$
@ -29,6 +29,9 @@ $Id$
brick magic tools, improved stamp tinter, and other fixes by:
Albert Cahalan <albert@users.sf.net>
Bilinear interpolation code based on an example by Christian Graus
( http://www.codeproject.com/cs/media/imageprocessing4.asp ).
* Graphics
@ -45,6 +48,7 @@ $Id$
* Brushes created using The GIMP
http://www.gimp.org/
* Starter Images
* Chicken

7
docs/CHANGES.txt
View file

@ -9,7 +9,7 @@ http://www.newbreedsoftware.com/tuxpaint/
$Id$
2006.October.26 (0.9.17)
2006.November.2 (0.9.17)
* Tool Improvements:
------------------
@ -17,6 +17,11 @@ $Id$
(Experimental; build with "make nosvg" to disable SVG support and
Cairo dependency.)
* Bilinear interpolation (smoothing) is done to small bitmap (PNG)
stamps when they are scaled up.
(Based on example code by Christian Graus:
http://www.codeproject.com/cs/media/imageprocessing4.asp )
* Documentation Improvements:
---------------------------
* Discussed SVG Stamps in "Extending Tux Paint."

129
src/tuxpaint.c
View file

@ -176,7 +176,9 @@ static scaleparams scaletable[] = {
#define CURSOR_BLINK_SPEED 500 /* Initial repeat speed for cursor */
#ifndef _GNU_SOURCE
#define _GNU_SOURCE /* for strcasestr() */
#endif
#include <stdio.h>
#include <stdlib.h>
@ -852,6 +854,10 @@ static SDL_Surface *thumbnail(SDL_Surface * src, int max_x, int max_y,
static SDL_Surface *thumbnail2(SDL_Surface * src, int max_x, int max_y,
int keep_aspect, int keep_alpha);
#ifndef NO_BILINEAR
static SDL_Surface *zoom(SDL_Surface * src, int new_x, int new_y);
#endif
@ -7493,7 +7499,7 @@ static SDL_Surface *do_loadimage(const char *const fname, int abort_on_error)
/* Load the image file: */
s = myIMG_Load(fname);
s = myIMG_Load((char *) fname);
if (s == NULL)
{
if (abort_on_error)
@ -8556,7 +8562,7 @@ static SDL_Surface *thumbnail2(SDL_Surface * src, int max_x, int max_y,
int x, y;
float src_x, src_y, off_x, off_y;
SDL_Surface *s;
Uint32 amask, tr, tg, tb, ta;
Uint32 tr, tg, tb, ta;
Uint8 r, g, b, a;
float xscale, yscale;
int tmp;
@ -8596,12 +8602,16 @@ static SDL_Surface *thumbnail2(SDL_Surface * src, int max_x, int max_y,
}
#ifndef NO_BILINEAR
if (max_x > src->w && max_y > src->h)
return(zoom(src, max_x, max_y));
#endif
/* Create surface for thumbnail: */
amask = ~(src->format->Rmask | src->format->Gmask | src->format->Bmask);
s = SDL_CreateRGBSurface(src->flags, /* SDL_SWSURFACE, */
max_x, max_y, src->format->BitsPerPixel, src->format->Rmask, src->format->Gmask, src->format->Bmask, src->format->Amask); /* amask); */
max_x, max_y, src->format->BitsPerPixel, src->format->Rmask, src->format->Gmask, src->format->Bmask, src->format->Amask);
if (s == NULL)
@ -8694,6 +8704,115 @@ static SDL_Surface *thumbnail2(SDL_Surface * src, int max_x, int max_y,
}
#ifndef NO_BILINEAR
/* Based on code from: http://www.codeproject.com/cs/media/imageprocessing4.asp
copyright 2002 Christian Graus */
static SDL_Surface *zoom(SDL_Surface * src, int new_w, int new_h)
{
SDL_Surface * s;
void (*putpixel) (SDL_Surface *, int, int, Uint32);
Uint32(*getpixel) (SDL_Surface *, int, int) =
getpixels[src->format->BytesPerPixel];
float xscale, yscale;
int x, y;
float floor_x, ceil_x, floor_y, ceil_y, fraction_x, fraction_y,
one_minus_x, one_minus_y;
float n1, n2;
float r1, g1, b1, a1;
float r2, g2, b2, a2;
float r3, g3, b3, a3;
float r4, g4, b4, a4;
Uint8 r, g, b, a;
/* Create surface for zoom: */
s = SDL_CreateRGBSurface(src->flags, /* SDL_SWSURFACE, */
new_w, new_h, src->format->BitsPerPixel,
src->format->Rmask,
src->format->Gmask,
src->format->Bmask,
src->format->Amask);
if (s == NULL)
{
fprintf(stderr, "\nError: Can't build zoom surface\n"
"The Simple DirectMedia Layer error that occurred was:\n"
"%s\n\n", SDL_GetError());
cleanup();
exit(1);
}
putpixel = putpixels[s->format->BytesPerPixel];
SDL_LockSurface(src);
SDL_LockSurface(s);
xscale = (float) src->w / (float) new_w;
yscale = (float) src->h / (float) new_h;
for (x = 0; x < new_w; x++)
{
for (y = 0; y < new_h; y++)
{
floor_x = floor((float) x * xscale);
ceil_x = floor_x + 1;
if (ceil_x >= src->w)
ceil_x = floor_x;
floor_y = floor((float) y * yscale);
ceil_y = floor_y + 1;
if (ceil_y >= src->h)
ceil_y = floor_y;
fraction_x = x * xscale - floor_x;
fraction_y = y * yscale - floor_y;
one_minus_x = 1.0 - fraction_x;
one_minus_y = 1.0 - fraction_y;
SDL_GetRGBA(getpixel(src, floor_x, floor_y), src->format,
&r1, &g1, &b1, &a1);
SDL_GetRGBA(getpixel(src, ceil_x, floor_y), src->format,
&r2, &g2, &b2, &a2);
SDL_GetRGBA(getpixel(src, floor_x, ceil_y), src->format,
&r3, &g3, &b3, &a3);
SDL_GetRGBA(getpixel(src, ceil_x, ceil_y), src->format,
&r4, &g4, &b4, &a4);
n1 = (one_minus_x * r1 + fraction_x * r2);
n2 = (one_minus_x * r3 + fraction_x * r4);
r = (one_minus_y * n1 + fraction_y * n2);
n1 = (one_minus_x * g1 + fraction_x * g2);
n2 = (one_minus_x * g3 + fraction_x * g4);
g = (one_minus_y * n1 + fraction_y * n2);
n1 = (one_minus_x * b1 + fraction_x * b2);
n2 = (one_minus_x * b3 + fraction_x * b4);
b = (one_minus_y * n1 + fraction_y * n2);
n1 = (one_minus_x * a1 + fraction_x * a2);
n2 = (one_minus_x * a3 + fraction_x * a4);
a = (one_minus_y * n1 + fraction_y * n2);
putpixel(s, x, y, SDL_MapRGBA(s->format, r, g, b, a));
}
}
SDL_UnlockSurface(s);
SDL_UnlockSurface(src);
return s;
}
#endif
// XOR must show up on black, white, 0x7f grey, and 0x80 grey.
// XOR must be exactly 100% perfectly reversable.