16 Image Core
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.
Draws image in dc at the position (dx,dy).
Recognizes the images that library handles.
Returns an image that either caches its drawing in the
method or doesn’t, depending on b
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%).
When the image has a bitmap-cache (which it does by default,
can disable it), this function
fills in the bitmap, doing the work to draw image into the bitmap.
Ordinarily, the image’s bitmap cache is computed the first time
the image is actually rendered.
Returns #t if i1 and i2 draw identically
and #f if they may draw the same or may draw differently.
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.)
The snipclass used by images (which are snip%
s) created by this library.
Not all image? values are snip%s, but those that are use this as