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seventoes
Joined: 02 Oct 2005
Posts: 79
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 Posted: Sun Dec 04, 2005 6:57 am Post subject: Image Scaling Algorithm with pg.c/.h? |
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Hey im back with another algorithm problem xD
This time i need something to scale the 16 bit image. I have absolutely no idea how to do this... and i've tried using google but cant seem to get any good results.
I am using pc.c/.h to blit my pictures (I would use the GU but i dont get it..) and i have already added alpha blending as an extra argument. Heres my function right now:
| Code: |
#define rgb2col(r, g, b) ((((b>>3) & 0x1F)<<10)+(((g>>3) & 0x1F)<<5)+(((r>>3) & 0x1F)<<0)+0x8000)
#define getR( c ) ( (c & 0x1f) << 3 )
#define getG( c ) ( ((c >> 5) & 0x1f ) << 3 )
#define getB( c ) ( ((c >> 10) & 0x1f) << 3 )
...
void pgBitBlt(unsigned long x,unsigned long y,unsigned long w,unsigned long h,unsigned long mag,const unsigned short *d, int t)
{
unsigned char *vptr0; //pointer to vram
unsigned char *vptr; //pointer to vram
unsigned long xx,yy,mx,my;
const unsigned short *dd;
int rB, gB, bB, rS, gS, bS, new_r, new_g, new_b; //color thingys
vptr0=(unsigned)pgGetVramAddr(x,y);
for (yy=0; yy<h; yy++) {
for (my=0; my<mag; my++) {
vptr=vptr0;
dd=d;
for (xx=0; xx<w; xx++) {
for (mx=0; mx<mag; mx++) {
if (*dd != 0x3e0) {
if (t != 255) {
rB = getR(*(unsigned short *)vptr);
gB = getG(*(unsigned short *)vptr);
bB = getB(*(unsigned short *)vptr);
rS = getR(*dd);
gS = getG(*dd);
bS = getB(*dd);
new_r = rB + (((rS - rB) * t) / 256);
new_g = gB + (((gS - gB) * t) / 256);
new_b = bB + (((bS - bB) * t) / 256);
*(unsigned short *)vptr = rgb2col(new_r,new_g,new_b);
}
else {
*(unsigned short *)vptr = *dd;
}
}
vptr+=PIXELSIZE*2;
}
dd++;
}
vptr0+=LINESIZE*2;
}
d+=w;
}
}
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How could i add a scaling factor to the function? |
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Brunni
Joined: 08 Oct 2005
Posts: 186
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| Posted: Sun Dec 04, 2005 7:50 am Post subject: |
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Speaking about algorithm only, scaling is very simple. In 32 bits without conversion it would look like this:
spr: sprite (32-bit pixels)
vptr: vram (32-bit pixels, LARG_BUF is buffer line width, LARG=width, HAUT=height)
x0, y0: drawing coordinates
lb, hb: base width (l), height (h)
l, h: new width and height
I've not tested it, but this gives you an idea.
| Code: | #define VIRGULE 16
void Rescale(unsigned short *spr, unsigned short *vptr, int x0, int y0, int lb, int hb, int l, int h) {
int x, y;
unsigned short *bits=vptr, *ptr, *spr2, *sprite;
int y_min, x_min, y_max, x_max;
long scaleX, scaleY, dstX, dstY;
int x1=x0+l, y1=y0+h;
//Clipping
if (x0>=0) x_min=x0;
else x_min=0;
if (y0>=0) y_min=y0;
else y_min=0;
if (x1<LARG) x_max=x1;
else x_max=LARG;
if (y1<HAUT) y_max=y1;
else y_max=HAUT;
scaleX=(lb<<VIRGULE)/l;
scaleY=(hb<<VIRGULE)/h;
dstY=scaleY*(y_min-y0);
for (y=y_min;y<y_max;y++) {
ptr=bits+LARG_BUF*y+x_min;
spr2=spr+lb*(dstY>>VIRGULE);
dstX=scaleX*(x_min-x0);
dstY+=scaleY;
for (x=x_min;x<x_max;x++) {
sprite=spr2+(dstX>>VIRGULE);
dstX+=scaleX;
if (*sprite==COLOR_TRANSPARENT) {
sprite++;
ptr++;
continue;
}
*ptr++=*sprite++;
}
}
} |
_________________
Sorry for my bad english
 Oldschool library for PSP - PC version released
Last edited by Brunni on Sun Dec 04, 2005 9:20 am; edited 2 times in total |
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urchin
Joined: 02 Jun 2005
Posts: 121
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| Posted: Sun Dec 04, 2005 8:24 am Post subject: |
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| Take a look at the sprites example in the SDK. Blitting and scaling a rect using GU is very easy. You get the option of filtering too. |
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seventoes
Joined: 02 Oct 2005
Posts: 79
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| Posted: Sun Dec 04, 2005 8:33 am Post subject: |
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| That might work, but what are LARG and HAUT? And would that work with 16 bit images? because thats what im using. |
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Brunni
Joined: 08 Oct 2005
Posts: 186
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| Posted: Sun Dec 04, 2005 9:19 am Post subject: |
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I changed the routine in my last post. With this one, it might work in 16-bit mode. LARG is the width of your sprite, and HAUT the height.
Typical 2x scaling for a 16x16 sprite on a 480x272 buffer (buffer width aligned to 512):
#define LARG 480
#define HAUT 272
#define LARG_BUF 512
Rescale(mysprite, myvideobuffer, 0, 0, 16, 16, 32, 32);
_________________
Sorry for my bad english
Oldschool library for PSP - PC version released |
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seventoes
Joined: 02 Oct 2005
Posts: 79
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| Posted: Wed Dec 07, 2005 11:07 am Post subject: |
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| urchin wrote: | | Take a look at the sprites example in the SDK. Blitting and scaling a rect using GU is very easy. You get the option of filtering too. |
I've tried that, but i just dont get it. If someone could write a SIMPLE example, maybe functions like gu_init(); or something...
| Quote: |
I changed the routine in my last post. With this one, it might work in 16-bit mode. LARG is the width of your sprite, and HAUT the height.
Typical 2x scaling for a 16x16 sprite on a 480x272 buffer (buffer width aligned to 512):
#define LARG 480
#define HAUT 272
#define LARG_BUF 512
Rescale(mysprite, myvideobuffer, 0, 0, 16, 16, 32, 32); |
Thanks, im trying that now. |
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dr_watson
Joined: 28 Nov 2005
Posts: 42
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| Posted: Wed Dec 07, 2005 12:39 pm Post subject: |
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Grab a copy of my little 2D game engine JGE (together with a small demo) and have a look of the related Gfx_RenderQuad() function. It uses Gu library for image rendering.
Engine source
And firmware 1.50 binary:
(You also need libpng and mikmodlib to build)
I'm still cleaning up the code and will do a "formal" posting at this forum soon, but at the meantime, you can check out the source and hope it can give you some hints :) |
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seventoes
Joined: 02 Oct 2005
Posts: 79
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| Posted: Thu Dec 08, 2005 5:35 am Post subject: |
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Thanks! The function worked brunni!
Ill take a look at your JGE thingy when i get home, im at school now. |
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dr_watson
Joined: 28 Nov 2005
Posts: 42
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seventoes
Joined: 02 Oct 2005
Posts: 79
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| Posted: Thu Dec 08, 2005 11:22 am Post subject: |
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| Thanks for the engine watson. I dont really understand C++, but ill try and work with it. |
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rinco
Joined: 21 Jan 2005
Posts: 255
Location: Canberra, Australia
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| Posted: Thu Dec 08, 2005 6:47 pm Post subject: |
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| SDL_rotozoom.c (part of SDL_gfx) can also stretch (and rotate). Currently it does not use any Gu functions, but it might one day. |
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