Designing Games with Game Maker - YoYo Games

image_yscale The vertical yscale. 1 is no scaling. You can use a value of -1
to flip the sprite vertically.
image_angle The angle with which the sprite is rotated. You specify this in
degrees, counterclockwise. A value of 0 indicates no rotation. This variable
can only be set in the Pro Edition!
image_alpha Transparency (alpha) value to use when drawing the image. A
value of 1 is the normal opaque setting; a value of 0 is completely
transparent.
image_blend Blending color used when drawing the sprite. A value of
c_white is the default. When you specify a different value the image is blended
with this color. This can be used to colorize the sprite on the fly. This variable
can only be set in the Pro Edition!
bbox_left* Left side of the bounding box of the instance in the room, as
defined by its image (taking scaling into account).
bbox_right* Right side of the bounding box of the instance in the room.
bbox_top* Top side of the bounding box of the instance in the room.
bbox_bottom* Bottom side of the bounding box of the instance in the room.
Backgrounds
Each room can have up to 8 backgrounds. Also it has a background color. All aspects of these
backgrounds you can change in a piece of code using the following variables (note that some
are arrays that range from 0 to 7, indicating the different backgrounds):
background_color Background color for the room.
background_showcolor Whether to clear the window in the background
color.
background_visible[0..7] Whether the particular background image is
visible.
background_foreground[0..7] Whether the background is actually a
foreground.
background_index[0..7] Background image index for the background.
background_x[0..7] X position of the background image.
background_y[0...7] Y position of the background image.
background_width[0...7]* Width of the background image.