DMDX Help.
Default BMP Multipliers Keyword
<DefaultBMPMultipliers F[,F]
[options]>
<dbm F[,F]
[options]>
Default Bitmap Multipliers, both switch and parameter. See <BMPMultipliers>
for multiplier description.
option can be used to set the stretch blt mode that affects how
colors are sampled when images are shrunk and can be one of the values in the
following table (YMMV but I find
HALFTONE is the useful mode but if your
machine is exceptionally slow by 2018 standards
COLORONCOLOR is passable). In addition to those options
STAT is available
(as of version 5.3.1.3) when
<dbm> is used in frame that forces the current
frame to use these multipliers and/or stretch mode (otherwise it/they would only
become active in the next frame). If
STAT is used in the parameter line with this
keyword all subsequent uses of it will be assumed to be
STAT. If
you wish to specify a default stretch blt mode without affecting how all images
are scaled you'll want to use a multiplier of 1 as in
<dbm 1 HALFTONE> and if you
wanted it active in the frame it occurred in you could use
<dbm 1 HALFTONE STAT>. See the
Bitmap Notes for a discussion on the stretch
blt mode. From
https://docs.microsoft.com/en-us/windows/desktop/api/Wingdi/nf-wingdi-setstretchbltmode:
| Value |
Meaning |
|
BLACKONWHITE
|
Performs a Boolean AND operation using the color values
for the eliminated and existing pixels. If the bitmap is a monochrome
bitmap, this mode preserves black pixels at the expense of white pixels.
|
|
COLORONCOLOR
|
Deletes the pixels. This mode deletes all eliminated
lines of pixels without trying to preserve their information.
|
|
HALFTONE |
Maps pixels from the source rectangle into blocks of
pixels in the destination rectangle. The average color over the
destination block of pixels approximates the color of the source pixels.
|
|
WHITEONBLACK
|
Performs a Boolean OR operation using the color values
for the eliminated and existing pixels. If the bitmap is a monochrome
bitmap, this mode preserves white pixels at the expense of black pixels.
|
The stretching mode defines how the system combines rows or columns of a
bitmap with existing pixels on a display device when an application calls the
StretchBlt function (that DMDX uses when
stretching bitmaps).
The BLACKONWHITE and WHITEONBLACK modes are typically used to preserve
foreground pixels in monochrome bitmaps. The COLORONCOLOR mode is typically used
to preserve color in color bitmaps.
The HALFTONE mode is slower and requires more processing of the source image
than the other three modes; but produces higher quality images.
Note that the default mode appears to
be BLACKONWHITE, didn't find anywhere that
defined it as such but visual inspection of the artifacts leads me to conclude
it's so.
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