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ne0h
Joined: 21 Feb 2008
Posts: 386
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 Posted: Fri Dec 18, 2009 6:48 am Post subject: Alpha blending to draw buffer? |
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It's that possible?
That's the function that I'm using:
| Code: |
void XgeFillScreenRect(XgeColor Color, int x0, int y0, int width, int height)
{
int skipX = PSP_LINE_SIZE - width;
int x, y;
XgeColor* data = XgeGetVramDrawBuffer() + x0 + y0 * PSP_LINE_SIZE;
for(y = 0; y < height; y++, data += skipX)
{
for(x = 0; x < width; x++, data++)
*data = Color;
}
}
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There's a way to do the same thing but with alpha?
Thanks,
ne0h
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a_noob
Joined: 17 Sep 2006
Posts: 97
Location: _start: jr 0xDEADBEEF
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| Posted: Fri Dec 18, 2009 10:36 am Post subject: |
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Its possible but it would be much better to use the GU.
alpha blending would be something like.
| Code: |
inline unsigned int RGBA(unsigned int R, unsigned int G, unsigned int B, unsigned int A)
{
return (unsigned int)((A & 0xFF) << 24 |
(R & 0XFF) << 16 |
(G & 0XFF) << 8 |
(B & 0XFF));
}
unsigned int alphaBlend(unsigned int a, unsigned int b){
float aa = 255.f/(a>>24&0xff);// A colors alpha channel as a float 0 - 1
float ba = 255.f/(b>>24&0xff);// B colors alpha channel as a float 0 - 1
char ar = aa * (a&0xff);//alpha influenced
char ag = aa * (a>>8&0xff);
char ab = aa * (a>>16&0xff);
char br = ba * (b&0xff);//alpha influenced
char bg = ba * (b>>8&0xff);
char bb = ba * (b>>16&0xff);
return RGBA(ar+br,ag+bg,ab+bb,(a+b)*255);
}
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ne0h
Joined: 21 Feb 2008
Posts: 386
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| Posted: Sat Dec 19, 2009 1:59 am Post subject: |
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Excuse me, I didn't explain my problem as I wanted...
When I use the function with alpha like this:
| Code: |
XgeFillScreenRect(0x50FF0000, X, Y, Width, Height);
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i won't get an rectange with trasparency....
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carl0sgs
Joined: 10 Dec 2009
Posts: 41
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| Posted: Sat Dec 19, 2009 3:30 am Post subject: |
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I think the function that a_noob wrote is for blending two colors.
Like this:
| Code: | | mixedColor = alphaBlend(RGB(100,200,50), RGB(200,100,150)); |
Should return the resulting color.
So you would have this function (i think):
| Code: | unsigned int RGBA(unsigned int R, unsigned int G, unsigned int B, unsigned int A)
{
return (unsigned int)((A & 0xFF) << 24 |
(R & 0XFF) << 16 |
(G & 0XFF) << 8 |
(B & 0XFF));
}
unsigned int alphaBlend(unsigned int a, unsigned int b){
float aa = 255.f/(a>>24&0xff);// A colors alpha channel as a float 0 - 1
float ba = 255.f/(b>>24&0xff);// B colors alpha channel as a float 0 - 1
char ar = aa * (a&0xff);//alpha influenced
char ag = aa * (a>>8&0xff);
char ab = aa * (a>>16&0xff);
char br = ba * (b&0xff);//alpha influenced
char bg = ba * (b>>8&0xff);
char bb = ba * (b>>16&0xff);
return RGBA(ar+br,ag+bg,ab+bb,(a+b)*255);
}
void XgeFillScreenRect(XgeColor Color, int x0, int y0, int width, int height)
{
int skipX = PSP_LINE_SIZE - width;
int x, y;
XgeColor* data = XgeGetVramDrawBuffer() + x0 + y0 * PSP_LINE_SIZE;
for(y = 0; y < height; y++, data += skipX)
{
for(x = 0; x < width; x++, data++)
*data = alphaBlend(Color,data);//We put the mixed color
}
} |
I hope that works! |
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ne0h
Joined: 21 Feb 2008
Posts: 386
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| Posted: Sat Dec 19, 2009 3:53 am Post subject: |
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O_O
omg...
Anyway, I'll try...
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carl0sgs
Joined: 10 Dec 2009
Posts: 41
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| Posted: Sat Dec 19, 2009 4:06 am Post subject: |
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OK, it works!
Thanks to both of you, you helped me a lot :-P
Now I can blend alpha images in multitasking :-)
@ne0h Good luck with Xplora, it is a really useful program :-D
Thanks again,
Carlos |
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ne0h
Joined: 21 Feb 2008
Posts: 386
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| Posted: Sat Dec 19, 2009 4:37 am Post subject: |
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Nevermind, resolved...
But now I get something like:
There's a way to do something like this funct but with only one color?
Like a monocrome texture?
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carl0sgs
Joined: 10 Dec 2009
Posts: 41
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| Posted: Sat Dec 19, 2009 5:13 am Post subject: |
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OK
You have to mix two colors because you want to put one color over the other one.
I don't know why that is not working, I let you this piece of code:
| Code: | #define RGBA(r, g, b, a) ((r)|((g)<<8)|((b)<<16)|((a)<<24)) //Use this instead of the other function
void blitAlphaImageToImage(int sx, int sy, int width, int height, Image* source, int dx, int dy, Image* destination)//With alpha
{
// TODO Blend! - Done! xD
Color* destinationData = &destination->data[destination->textureWidth * dy + dx];
int destinationSkipX = destination->textureWidth - width;
Color* sourceData = &source->data[source->textureWidth * sy + sx];
int sourceSkipX = source->textureWidth - width;
int x, y;
for (y = 0; y < height; y++, destinationData += destinationSkipX, sourceData += sourceSkipX) {
for (x = 0; x < width; x++, destinationData++, sourceData++) {
Color color = *sourceData;
*destinationData = alphaBlend(*destinationData,color);
}
}
} |
This is what works for me, I haven't tested the rectangle function, sorry :-S |
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carl0sgs
Joined: 10 Dec 2009
Posts: 41
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| Posted: Sat Dec 19, 2009 5:16 am Post subject: |
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| ne0h wrote: | Nevermind, resolved...
But now I get something like:
There's a way to do something like this funct but with only one color?
Like a monocrome texture? |
No idea of how did you got that :-S
It is not possible to do that alpha blending without using two colors, maybe with the GU, but that would do the same thing really.
Sorry :-S |
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ne0h
Joined: 21 Feb 2008
Posts: 386
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| Posted: Sat Dec 19, 2009 5:20 am Post subject: |
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I don't use images but fillscreenrect only for memory purposes...
I want to find a way to draw an alpha rectangle on the screen,
just like sceGuTexImage, but without loading something like 1MB of image...
Anyway sorry for misunderstanding with the two colors and thanks both.
ne0h
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carl0sgs
Joined: 10 Dec 2009
Posts: 41
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| Posted: Sat Dec 19, 2009 5:31 am Post subject: |
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| I think you should change the alpha values |
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a_noob
Joined: 17 Sep 2006
Posts: 97
Location: _start: jr 0xDEADBEEF
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| Posted: Sat Dec 19, 2009 6:55 am Post subject: |
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oh its my bad for the b alpha you need to do 1 - the alpha. So
| Code: |
unsigned int alphaBlend(unsigned int a, unsigned int b){
float aa = 255.f/(a>>24&0xff);// A colors alpha channel as a float 0 - 1
float ba = 1.f-(255.f/(b>>24&0xff));// B colors alpha channel as a float 0 - 1
unsigned char ar = aa * (a&0xff);//alpha influenced
unsigned char ag = aa * (a>>8&0xff);
unsigned char ab = aa * (a>>16&0xff);
unsigned char br = ba * (b&0xff);//alpha influenced
unsigned char bg = ba * (b>>8&0xff);
unsigned char bb = ba * (b>>16&0xff);
return RGBA(ar+br,ag+bg,ab+bb,(a+b)*255);
} |
should do the trick.
I do advise switching to the GU as this is terribly slow on the CPU, you need to do this calculation for each pixel :/ where as the GPU has built in hardware blending procedures which are extremely fast.
-=EDIT=-
Oh crap and the psp uses 0xAABBGGRR not 0xAARRGGBB so this is the updated RGBA func
| Code: | unsigned int RGBA(unsigned int R, unsigned int G, unsigned int B, unsigned int A)
{
return (unsigned int)((A & 0xFF) << 24 | (B & 0XFF) << 16 | (G & 0XFF) << 8 | (R & 0XFF));
} |
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carl0sgs
Joined: 10 Dec 2009
Posts: 41
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| Posted: Sat Dec 19, 2009 7:44 am Post subject: |
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Good!
Thanks for the updated function ;-) |
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Raphael
Joined: 17 Jan 2006
Posts: 646
Location: Germany
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| Posted: Sat Dec 19, 2009 8:06 am Post subject: |
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Just for note: It should be 1-aalpha, if anything, for the common alpha blending behaviour.
Still, this software solution is stupid for anything else but learning how alpha blending works.
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ne0h
Joined: 21 Feb 2008
Posts: 386
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| Posted: Sun Dec 20, 2009 3:48 am Post subject: |
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I would like to use sceGu, but how?
I've never used very much sceGu...
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Raphael
Joined: 17 Jan 2006
Posts: 646
Location: Germany
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| Posted: Sun Dec 20, 2009 5:30 am Post subject: |
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pspsdk/samples/gu is your first source of information. Afterwards, there are lots of open source graphical engines available, that you can learn from, like OSlib or triEngine to name only two.
Using gu is very simple. It's just a matter of a little time investment to learn the concepts of a state machine and a very basic graphics api. If you have some pre-knowledge on OpenGL it's easy as cake.
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http://wiki.fx-world.org - VFPU documentation wiki
Alexander Berl |
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Torch
Joined: 28 May 2008
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