SDL accessing pixel data of SDL_Surface - c++

Question

I want to manipulate the color of loaded images but I am having trouble when I try to backup the pixel data. My code looks something like this:
Uint32* pixels, oriPixels;
SDL_Surface* image;
void BackupPixelData()
{
pixels = (Uint32*)image->pixels;
oriPixels = new Uint32[image->w * image->h];
for (int i = 0; i < image->w * image->h; i++)
{
oriPixels[i] = pixels[i]; //This causes an access violation midway through
*(oriPixels + i) = *(pixels + i); //Using this method does not cause any crash, but the image will have artifacts
}
}
I can get the code to work by changing oriPixels into a vector of Uint32, and I haven't experienced any issues doing that (the image can be restored to the original color using the oriPixels).
What should I do to properly load the pixel data?
The image is in 32 bits.

Answer 1

You must take into account data alignment. Rows may be padded depending on the surface format.
Check the documentation about the pitch field of the SDL_Surface for more details https://wiki.libsdl.org/SDL_Surface.
You get the access violation because the memory buffer size is not width * height but actually pitch * height.