Designing Games with Game Maker - YoYo Games

different types of images can be dealt with. 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.
The function returns the index of the new background that you can then use to
draw it or to assign it to the variable background_index[0] to make it visible in
the current room. When an error occurs -1 is returned.
background_add_alpha(fname,preload) Adds the image stored in the
file fname to the set of background 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.
background_replace(ind,fname,transparent,smooth,preload)
Same as above but in this case the background with index ind is replaced. The
function returns whether it is successful. When the background is currently
visible in the room it wil be replaced also.
background_replace_alpha(ind,fname,preload) Same as above but in
this case the file has an alpha channel.
background_create_color(w,h,col,preload) Creates a background of
the given size and with the given color. It returns the index of the new
background. When an error occurs -1 is returned.
background_create_gradient(w,h,col1,col2,kind,preload)
Creates a gradient filled background of the given size. col1 and col2 indicate
the two colors. kind is a number between 0 and 5 indicating the kind of
gradient: 0=horizontal 1=vertical, 2= rectangle, 3=ellipse, 4=double
horizontal, 5=double vertical. It returns the index of the new background.
When an error occurs -1 is returned.
background_create_from_screen(x,y,w,h,transparent,smooth,pr
eload) Creates a background by copying the given area from the screen. This
makes it possible to create any background you want. Draw the image on the
screen using the drawing functions and next create a background from it. (If
you don't do this in the drawing event you can even do it in such a way that it
is not visible on the screen by not refreshing the screen.) The other
parameters are as above. The function returns the index of the new
background. A work of caution is required here. Even though we speak about
the screen, it is actually the drawing region that matters. The fact that there is
a window on the screen and that the image might be scaled in this window