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lifecat9
Joined: 29 Aug 2008
Posts: 7
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 Posted: Mon Sep 15, 2008 7:16 pm Post subject: How to cover the PNG image with another PNG image? |
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My Code :
| Code: |
#include <sdl.h>
#include <sdl_image.h>
void main(){
Surf_Display = SDL_SetVideoMode(400,400, 32, SDL_HWSURFACE | SDL_DOUBLEBUF));
SDL_Surface* png1 = IMG_Load("png1.png");
SDL_Surface* png2 = IMG_Load("png2.png");
SDL_BlitSurface(png1, NULL, png2,NULL);
SDL_BlitSurface(png2, NULL,Surf_Display,NULL);
SDL_Flip(Surf_Display);
}
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ne0h
Joined: 21 Feb 2008
Posts: 386
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| Posted: Tue Sep 16, 2008 12:15 am Post subject: |
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You are blitting your image in the pn2 surface!
| Code: |
#include <sdl.h>
#include <sdl_image.h>
void main(){
Surf_Display = SDL_SetVideoMode(400,400, 32, SDL_HWSURFACE | SDL_DOUBLEBUF));
SDL_Surface* png1 = IMG_Load("png1.png");
SDL_Surface* png2 = IMG_Load("png2.png");
SDL_BlitSurface(png2, NULL,Surf_Display,NULL);
SDL_BlitSurface(png1, NULL, Surf_Display,NULL);
SDL_Flip(Surf_Display);
}
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Try this... |
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lifecat9
Joined: 29 Aug 2008
Posts: 7
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| Posted: Tue Sep 16, 2008 2:43 am Post subject: |
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| ne0h wrote: | You are blitting your image in the pn2 surface!
| Code: |
#include <sdl.h>
#include <sdl_image.h>
void main(){
Surf_Display = SDL_SetVideoMode(400,400, 32, SDL_HWSURFACE | SDL_DOUBLEBUF));
SDL_Surface* png1 = IMG_Load("png1.png");
SDL_Surface* png2 = IMG_Load("png2.png");
SDL_BlitSurface(png2, NULL,Surf_Display,NULL);
SDL_BlitSurface(png1, NULL, Surf_Display,NULL);
SDL_Flip(Surf_Display);
}
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Try this... |
That's a good idea,think you!
But the Surf_Display will lost png1 and png2's alpha informats(suppose Surf_Display is transparence).How to save alpha informats? |
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Raphael
Joined: 17 Jan 2006
Posts: 646
Location: Germany
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lifecat9
Joined: 29 Aug 2008
Posts: 7
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| Posted: Tue Sep 16, 2008 10:10 pm Post subject: |
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| Raphael wrote: | | Short answer: you simply can't on PSP |
?????
Yes!I cross out some codes;
this is SDL problem,of course you can use SDL in PSP. |
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Raphael
Joined: 17 Jan 2006
Posts: 646
Location: Germany
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| Posted: Wed Sep 17, 2008 1:47 am Post subject: |
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OK, a little longer answer to make it clear:
You can't write to alpha on PSP (hardware limitation unless SDL would use a software method for blended blitting which is just slow), hence why you can't save the alpha part of png1 into png2 and then blit that to screen.
You have to do as ne0h suggested and just blit your images to screen directly in the proper order.
_________________
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Alexander Berl |
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