调整图片大小SDL / c ++

Question

I have an image, I want to scale it down so that it's not its original size.

SDL_Rect bulletRect;
bulletRect.x = 10;
bulletRect.y = 10;
bulletRect.w = 10;
bulletRect.h = 10;

SDL_Surface *bullet = IMG_Load("/Users/tonymichaelsen/Documents/documents/Xcode-projects/c++/c++/bullet.png");
Uint32 colorKeyBullet = SDL_MapRGB(bullet->format, 255, 255, 255);
SDL_SetColorKey(bullet, SDL_SRCCOLORKEY, colorKeyBullet);

Blitted:

if (drawBullet) //bool set to true in key event
{
    SDL_BlitSurface(bullet, NULL, screen, &bulletRect);
}
SDL_Flip(screen);

The only thing that changes is when I'm changing the x,y values of the bullet (image). When I'm changing the w,h it doesn't change and the color key has no effect.
Whats wrong?

Answer 1

SDL_BlitSurface doesn't perform scaling, it requires that the destination size be equal to the source size.

You probably want to look into the SDL-OpenGL integration, which will allow you to use the texturing functionality of your video card for rescaling sprites.

Answer 2

Instead of NULL you could pass it a new rect with the size you need. SDL_BlitSurface(bullet, NULL, screen, &bulletRect);

int SDL_BlitSurface(SDL_Surface *src, SDL_Rect *srcrect, SDL_Surface *dst, SDL_Rect *dstrect);

"The width and height in srcrect determine the size of the copied rectangle. Only the position is used in the dstrect (the width and height are ignored)."

Here it explains how it works:

http://www.libsdl.org/docs/html/sdlblitsurface.html