3 Cache-image Snip

(require mrlib/cache-image-snip)

The mrlib/cache-image-snip library provides the core data structure for DrScheme’s "image.ss" teachpack. Images in the "image.ss" teachpack are instances of the cache-image-snip% class.

The library also defines a new type, argb, that represents a bitmap, but with alpha values. It has a maker, two selectors, and a predicate.

cache-image-snip% : class?

superclass: snip%

(send a-cache-image-snip get-argb) → argb?

Returns a pixel array for this image, forcing it to be computed.

(send a-cache-image-snip get-argb-proc)

→ (argb? exact-integer? exact-integer? . -> . void?)

Returns a procedure that fills in an argb with the contents of this image at the given offset

(send a-cache-image-snip get-argb/no-compute)

→ (or/c false/c argb?)

Returns a pixel array for this image or #f if it has not been computed yet.

(send a-cache-image-snip get-bitmap)

→ (or/c false/c (is-a?/c bitmap%))

Builds (if not yet built) a bitmap corresponding to this snip and returns it.

If the width or the height of the snip is 0, this method return #f.

(send a-cache-image-snip get-dc-proc)

→ (or/c false/c ((is-a?/c dc<%>) real? real? -> void?))

Either returns false, or a procedure that draws the contents of this snip into a dc.

(send a-cache-image-snip get-pinhole)   →   real?   real?

Returns the pinhole coordinates for this image, counting from the top-left of the image.

(send a-cache-image-snip get-size)

→   exact-nonnegative-integer? exact-nonnegative-integer?

Returns the width and height for the image.

snip-class : (is-a?/c snip-class%)

This snipclass is used for saved cache image snips.

(make-argb vectorof width height) → argb?

vectorof : (integer-in 0 255)

width : exact-nonnegative-integer?

height : exact-nonnegative-integer?

Constructs a new argb value. The vector has four entries for each pixel, an alpha, red, green, and blue value. The int specifies the width of the image; the height is the size of the vector, divided by 4, divided by the width.

(argb-vector argb) → (vectorof (integer-in 0 255))

argb : argb?

Extracts the vector from argb.

(argb-width argb) → exact-nonnegative-integer?

argb : argb?

Extracts the width from argb.

(argb-height argb) → exact-nonnegative-integer?

argb : argb?

Extracts the height from argb.

(argb? v) → boolean?

v : any/c

Returns #t if v is an argb, #f otherwise.

(overlay-bitmap dest dx dy img mask) → void?

dest : argb?

dx : exact-integer?

dy : exact-integer?

img : (is-a?/c bitmap%)

mask : (is-a?/c bitmap%)

Changes argb, overlaying img with masking based on mask at (dx, dy) from the top-left.

(build-bitmap draw width height) → (is-a?/c bitmap%)

draw : ((is-a?/c dc<%>) . -> . any)

width : (integer-in 1 10000)

height : (integer-in 1 10000)

Builds a bitmap of size width by height, using the procedure draw to render the bitmap content into the given dc<%>.

(flatten-bitmap bitmap) → (is-a?/c bitmap%)

bitmap : (is-a?/c bitmap%)

Builds a new bitmap that flattens the original bitmap with its mask (as determined by get-loaded-mask in bitmap%), producing a bitmap that has no mask, and looks the way that bitmap would draw (when drawn with the mask) onto a white background.

(argb->cache-image-snip argb dx dy) → (is-a?/c cache-image-snip%)

argb : argb?

dx : real?

dy : real?

Builds a new cache-image-snip% based on the contents of argb, using dx and dy as the pinhole.

(argb->bitmap argb) → (or/c false/c (is-a?/c bitmap%))

argb : argb?

Builds a bitmap that draws the same way as argb; the alpha pixels are put into the bitmap’s get-loaded-mask bitmap.

If the width or height of argb is 0, this returns #f.