SDL 1.2 scaling options

[eyecreate]

I'm working on porting a SDL 1.2 game that was coded to render at 320x240. I saw some online discussion about using rotozoom to scale and blit onto another larger video surface, but wasn't sure a) if this is the best way for performance or B) there is another solution that doesn't require poking around too deep into the bliting/rendering code.

 

[slaeshjag]

You can use the hardware scaler supported by notaz's SDL.

http://www.gp32x.de/board/index.php?/topic/59528-prison-break-port/page-2#entry950166

You don't need the library though, it ships with the system now afaik.

 

[mcobit]

No manual codechanges required. Notaz added a hardwarescaler to the sdl in the Pandora.


Set the following variables in your startupscript:


export SDL_VIDEODRIVER=omapdss


export SDL_OMAP_LAYER_SIZE=fullscreen


Read more here:

http://notaz.gp2x.de/cgi-bin/gitweb.cgi?p=sdl_omap.git;a=blob;f=README.OMAP

 

[eyecreate]

Thanks! that was way less painful than I thought it may be.

 

[ekianjo]

Thanks! that was way less painful than I thought it may be.

This was mentioned, by the way, in the tutorial for porting Arkanoid on Pandoralive, written by Ptitseb. Have a look at it

 

[PokeParadox]

Another alternative is to use the Scale 2x algorithm. It's faster than SDL_gfx's rotozoom functions and smooths out the jaggies. I used it for CromoZome.


HW scaler is probably easiest and with next to no performance overhead.

 

[sebt3]

Another alternative is to use the Scale 2x algorithm. It's faster than SDL_gfx's rotozoom functions

about 10 fold faster. rotozoom is the slowest zoom I ever seen in my life

 

[notaz]

Not everyone likes the scaling algos though, some prefer plain nearest-neighbor scaler.

 

[PokeParadox]

Not everyone likes the scaling algos though, some prefer plain nearest-neighbor scaler.

Oh absolutely! I just thought it would be useful to provide alternative answers as some people might want the output to be smoothed also.

 

[M-HT]

Except that Scale2x doesn't use any smoothing at all.

It only uses colors from original image.

 

[_wb_]

Scale2x or just nearest neighbor are good for pixel art, especially the old pixel art with a palette of only [some low power of two] colors.

For high-color picture-like images, smooth/blurry scaling (i.e. bilinear or bicubic interpolation or something like that) is best.

The hardware scaler, which is used in notaz' SDL, can be configured to do nearest neighbor or smooth scaling. Scale2x or any other pixel art scaling algorithm can be a good alternative in some cases, but the downside is that it cannot be done in hardware (so there's some overhead), and it tends to have artifacts: e.g. fonts tend to look quite different/weird with such scaling.