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doc clarifications

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This commit is contained in:
Matthew Flatt 2011-08-22 12:27:06 -06:00
parent 36d3cc69db
commit a0ba7eb10c
2 changed files with 8 additions and 3 deletions
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9
collects/scribblings/draw/bitmap-dc-class.scrbl
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@ -62,16 +62,19 @@ Gets a rectangle of pixels in the bitmap, subject to the same rules
same method directly, so it is not necessary to select a bitmap into same method directly, so it is not necessary to select a bitmap into
a DC to extracts its pixel values. a DC to extracts its pixel values.
The pixel RGB values are copied into @racket[pixels]. The first byte The pixel RGB values and alphas are copied into @racket[pixels]
(or just alpha values if @racket[just-alpha?] is true). The first byte
represents an alpha value of the pixel at (@racket[x], @racket[y]), represents an alpha value of the pixel at (@racket[x], @racket[y]),
the second byte represents a red value of the pixel at (@racket[x], the second byte represents a red value of the pixel at (@racket[x],
@racket[y]), the third byte is the blue value, etc. In this way, the @racket[y]), the third byte is the green value, etc. In this way, the
first @math{@racket[width] * @racket[height] * 4} bytes of first @math{@racket[width] * @racket[height] * 4} bytes of
@racket[pixels] are set to reflect the current pixel values in the @racket[pixels] are set to reflect the current pixel values in the
DC. The pixels are in row-major order, left to right then top to DC. The pixels are in row-major order, left to right then top to
bottom. bottom.
If @racket[just-alpha?] is false, if the bitmap does not have an alpha If the bitmap has an alpha channel, then the alpha value for each pixel
is always set in @racket[pixels].
If @racket[just-alpha?] is false and the bitmap does not have an alpha
channel, then the alpha value for each pixel is set to 255. If channel, then the alpha value for each pixel is set to 255. If
@racket[just-alpha?] is true, then @italic{only} the alpha value is set @racket[just-alpha?] is true, then @italic{only} the alpha value is set
for each pixel; if the bitmap has no alpha channel, then the alpha for each pixel; if the bitmap has no alpha channel, then the alpha

2
collects/scribblings/draw/svg-dc-class.scrbl
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@ -6,6 +6,8 @@
Similar to @racket[post-script-dc%], but generates a SVG (scalable Similar to @racket[post-script-dc%], but generates a SVG (scalable
vector graphics) file instead of a PostScript file. vector graphics) file instead of a PostScript file.
@|PrintNote|
@defconstructor[([width (and/c real? (not/c negative?))] @defconstructor[([width (and/c real? (not/c negative?))]
[height (and/c real? (not/c negative?))] [height (and/c real? (not/c negative?))]
[output (or/c path-string? output-port?)] [output (or/c path-string? output-port?)]