sprite_add(fname,imgnumb,precise,transparent,smooth,preload,xorig,yorig) Adds the image stored in the file fname to the set of sprite resources. Many different image file types can be dealt with. When the image is not a gif image it can be a strip containing a number of subimages for the sprite next to each other. Use imgnumb to indicate their number (1 for a single image). For (animated) gif images, this argument is not used; the number of images in the gif file is used. precise indicates whether precise collision checking should be used. transparent indicates whether the image is partially transparent. smooth indicates whether to smooth the edges. preload indicates whether to preload the image into texture memory. xorig and yorig indicate the position of the origin in the sprite. The function returns the index of the new sprite that you can then use to draw it or to assign it to the variable sprite_index of an instance. When an error occurs -1 is returned.
sprite_add_alpha(fname,imgnumb,precise,preload,xorig,yorig) Adds the image stored in the file fname to the set of sprite resources, but this time the file has an alpha channel to indicate transparency (as for example in .png files). The arguments are the same as above (but two are missing as they are not relevant in this case). When an error occurs -1 is returned.
sprite_replace(ind,fname,imgnumb,precise,transparent,smooth,preload,xorig,yorig) Same as above but in this case the sprite with index ind is replaced. The function returns whether it is successful.
sprite_replace_alpha(ind,fname,imgnumb,precise,preload,xorig,yorig) Same as above but in this case the file has an alpha channel. The function returns whether it is successful.