[SDL] VRAM, RAM & transparency

Engines and Middleware Programming

Started by Ptival June 12, 2005 12:26 PM

7 comments, last by Ptival 18 years, 10 months ago

122

Author

June 12, 2005 12:26 PM

Hi ! I'm french so excuse my faults please :) Surfacetemp is a Software SDL_Surface* (RAM) Vramtemp is a Hardware SDL_Surface* (VRAM), filled in black (0,0,0) I've got a SDL_LoadBMP() who loades a bitmap in Surfacetemp. I want to copy this bitmap in Vramtemp and set it the Color Key (0,255,0)[GREEN] In the first time, I tried to blit Surfacetemp on Vramtemp, then set the color key of Vramtemp :


SDL_BlitSurface(Surfacetemp,NULL,Vramtemp,&Recttemp);
SDL_SetColorKey(Vramtemp, SDL_SRCCOLORKEY, SDL_MapRGB(Vramtemp->format, 0, 255, 0));

The bitmap is well blitted on Vramtemp, but the colorkey is not transparent in game ! Then I tried to set the colorkey green on Surfacetemp, to blit Surfacetemp on Vramtemp, then to set the colorkey black on Vramtemp :


SDL_SetColorKey(Surfacetemp, SDL_SRCCOLORKEY, SDL_MapRGB(Surfacetemp->format, 0, 255, 0));
SDL_BlitSurface(Surfacetemp,NULL,Vramtemp,&Recttemp);
SDL_SetColorKey(Vramtemp, SDL_SRCCOLORKEY, SDL_MapRGB(Vramtemp->format, 0, 0, 0));

This second method works, but I wonder why the first didn't work...This method doesn't satisfy me much :Is there a way to do it like I wanted to ? (I hope my english is understandable -___-) Thank you ! :)

Drew_Benton

1,865

June 12, 2005 01:05 PM

I'm thinking the problem is because the image loaded and the destination are not of the same format, so try something like this:

// Load the BMPSDL_Surface* Surfacetemp = SDL_LoadBMP("YourBMP");// Convert to the Vramtemp surface formatSDL_Surface* temp2 = SDL_ConvertSurface(Surfacetemp,Vramtemp->format,Vramtemp->flags );// Blit this onto the Vramtemp surfaceSDL_BlitSurface(Surfacetemp,NULL,Vramtemp,&Recttemp);// Now set the color keySDL_SetColorKey(Vramtemp, SDL_SRCCOLORKEY, SDL_MapRGB(Vramtemp->format, 0, 255, 0));

Here is the doc page for SDL_ConvertSurface. I'm not sure if the Vramtemp->flags is correct, so you may have to mess around with that.

Another option is to make sure that the Vramtemp is of the same display format as the main screen, then convert the BMP into the main screens format, then blit, and set transparency.

Vramtemp = SDL_DisplayFormat( SDL_GetVideoSurface() );// Load the BMPSDL_Surface* Surfacetemp = SDL_LoadBMP("YourBMP");// Convert to the Vramtemp surface formatSDL_Surface* temp2 = SDL_DisplayFormat(SDL_GetVideoSurface());// Blit this onto the Vramtemp surfaceSDL_BlitSurface(Surfacetemp,NULL,Vramtemp,&Recttemp);// Now set the color keySDL_SetColorKey(Vramtemp, SDL_SRCCOLORKEY, SDL_MapRGB(Vramtemp->format, 0, 255, 0));

Here's the main doc function listing for reference for other functions. Good luck!

Ptival

122

Author

June 12, 2005 03:58 PM

I think I found a best solution using :

SDL_Surface*Vramtemp = SDL_AllocSurface(SDL_HWSURFACE|SDL_SRCCOLORKEY, Ramtemp->w, Ramtemp->h, 24, 0, 255, 0, 255);

Thanks for your help ;)

DvDmanDT

1,951

June 12, 2005 04:10 PM

Unless I'm misstaken, you use 24 bits, which is slow (not sure how slow, but just about everyone will warn you about it).. Make sure all surfaces are the same format..

Axenation

127

June 13, 2005 01:58 AM

I've been down this road before. Your original surface is colorkeyed, so when you blit it onto the second surface it only blits the non-colorkeyed pixels. The colorkeyed pixels will be black or randomized on your destination surface. You have to turn off colorkeying when copying surfaces.

psuedo code

function CopySurface(origSurface, destSurface){    origColorKey = origSurface->colorkey;    turnOffColorkey(origSurface);    blitSurface(origSurface, destSurface)    // set colorkey    origSurface->colorKey = origColorKey;    destSurface->colorKey = origColorKey;}

Now I get a cookie!

Ptival

122

Author

June 14, 2005 10:41 AM

€dit : The code was bugged, sorry :
[Edited by - Ptival on June 15, 2005 3:41:52 AM]

Ptival

122

Author

June 15, 2005 03:16 AM

Finally I didn't succeed...

Has anyone ever load an image in VideoRAM and Colorkey-d it ?

Kylotan

10,510

June 15, 2005 06:46 AM

Any reason why you don't just use SDL_DisplayFormat on the loaded graphics and forget about trying to explicitly handle video memory?

Ptival

122

Author

June 15, 2005 09:36 AM

Well, I tried this :

http://www.rafb.net/paste/results/Hv551q50.html

But the colorkey does'nt work :(Although if I force the loading in RAM, the color key is well put)

€dit -> Finally it works !

I've just deleted the second ColorKey :)

Thanks to evetyone ;)

[Edited by - Ptival on June 15, 2005 11:36:09 AM]

[SDL] VRAM, RAM & transparency

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[SDL] VRAM, RAM & transparency

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