16 Image Core
| (require mrlib/image-core) | package: gui-lib |
This library is the core part of the 2htdp/image library that DrRacket links into the namespace of all languages that it runs. This ensures that minimal support for these images are the same in all languages, specifically including support for printing the images and constructing the core data structures making up an image.
procedure
(render-image image dc dx dy) → void?
image : image? dc : (is-a?/c dc<%>) dx : real? dy : real?
procedure
(un/cache-image image b) → image?
image : image? b : any/c
Not all image? values have special caching capabilities; in those cases, this returns a copy of the value if it is a snip%; otherwise it returns the value itself (if it isn’t a snip%).
procedure
(compute-image-cache image) → void?
image : image?
Ordinarily, the image’s bitmap cache is computed the first time the image is actually rendered.
procedure
(definitely-same-image? i1 i2) → boolean?
i1 : image? i2 : image?
This test is intended to be cheaper than a full equality comparison. It is also used by the implementation of equal? on images to short-circuit the full check. (The full check draws the two images and then compares the resulting bitmaps.)
value
Not all image? values are snip%s, but those that are use this as their snip-class%.