zgv.1

一个利用SDL语言来实现svgalib函数的示例程序

.RS
Toggle shuffling (randomising) of slideshows. See \fBSlideshows\fR.
.PP
.RE
`\fBL\fR'
.RS
Toggle looping in slideshows. See \fBSlideshows\fR.
.PP
.RE
`\fBAlt-m\fR'
.RS
Toggle use of `magic numbers' (identifiers at the start of a file) to
pick which files in a directory to list in the selector. The usual
method of doing this is based on the file's extension (see \fBFile Type
Identification\fR, which is much faster but won't catch e.g. files without
extensions.
.PP
.RE
`\fBc\fR'
.RS
If the file selector is running in 16-colour mode (it usually doesn't
unless zgv has no choice --- see \fB16-colour File Selector\fR), toggle
between greyscale (default) and colour thumbnails.
.RE
.PP
.SH "OTHER FILE SEL COMMANDS"
There are some other commands in the file selector which don't easily
fit anywhere else. Here they are:
.PP
`\fBDelete\fR'
.RS
Delete (only) the file the cursor is on. Asks for confirmation (unless
this is disabled, see \fBConfiguring zgv\fR). It also deletes the file's
thumbnail, if it has one. See \fBCopying/Moving/Deleting Files\fR, for a
more general command which deletes all tagged files.
.PP
.RE
`\fB:\fR'
.RS
Show various details about the file the cursor is on; the (full)
filename, the size in kilobytes, width/height if recorded in any
thumbnail, last-modified date, etc. You can also use the `\fB;\fR' key to
get this.
.PP
.RE
`\fBAlt-f\fR'
.RS
Show the number of (picture) files in the current directory, and the
number of tagged files (see \fBTagging\fR).
.PP
.RE
`\fB^L\fR'
.RS
.RE
`\fB^R\fR'
.RS
Rescan the directory contents, and redraw the screen.
.PP
.RE
`\fBK\fR'
.RS
Kill mouse --- disable mouse for the rest of this zgv session. (It
prompts to check if you really want to do so.) This can be useful if you
have the mouse enabled in a config file, so that zgv always starts up
with the mouse on, but you're currently using just the keyboard. In such
a situation the mouse pointer can be a bit annoying. This command lets
you disable the mouse completely for the current zgv process.
.RE
.PP
.SH "SHOWING MORE FILES"
The file selector normally runs at a relatively low resolution
(640x480), meaning it can only show 20 thumbnails at once. This keeps
the selector running at a reasonable speed even on slow machines.
.PP
If you have a faster machine, however, and your video card has
256-colour modes with higher resolutions than 640x480 (see \fBVideo
Modes\fR), you may want to see more thumbnails onscreen at once.
.PP
(zgv tends not to look as `right' in such modes as it does in the usual
640x480, but apart from that it's much the same.)
.PP
`\fBF1\fR'
.RS
Select 640x480 mode. This is the default.
.PP
.RE
`\fBF2\fR'
.RS
Select 800x600 mode.
.PP
.RE
`\fBF3\fR'
.RS
Select 1024x768 mode.
.PP
.RE
`\fBF4\fR'
.RS
Select 1280x1024 mode.
.RE
.PP
If you want to change the default mode used in the file selector, use
the \fIfs-start-mode\fR config file setting (see \fBConfiguring zgv\fR).
For example, to use 800x600 by default, you'd use \fIfs-start-mode
800 600 8\fR.
.PP
Note these modes are subject to the same checks as in the viewer --- in
particular, this means that the file selector obeys the viewer's
\fImode-good\fR, \fImode-bad\fR, etc. settings. See \fBConfig
Variables\fR.
.PP
Finally, if you have no 640x480 256-colour mode, or if
\fIforce-fs-16col\fR has been set, the 640x480 16-colour mode is all
that is available.
.PP
.SH "16-COLOUR FILE SELECTOR"
The file selector normally operates in a 256-colour mode (by default,
the 640x480 one). However, the original VGA cards didn't have this mode,
and SVGA cards not supported by svgalib won't have it as far as zgv is
concerned either.
.PP
For such cards, zgv supports a more limited and slower file selector
which works in 640x480 16-colour mode. It should be easy to tell which
zgv is using --- if thumbnails appear in monochrome rather than colour
(and the files are colour pictures ;-)) then it's running in 16-colour
mode. (Another hint is that 16-colour mode has an extra border around
the edge of the screen which 256-colour mode probably won't have.)
.PP
As you might imagine, having 240 fewer colours makes things difficult.
The default way of coping with this is the greyscale thumbnails (eleven
grey levels are used), which are reasonably fast and quite faithful to
the originals. If you'd prefer less accurate --- but colour ---
thumbnails (eight colours are used, with dithering and increased
contrast), you can press `\fBc\fR' to toggle between the two, or set zgv
up to default to using colour thumbnails instead with
\fIfs-16col-colour-thumbnails on\fR in a config file
(see \fBConfiguring zgv\fR).
.PP
(For those of you out there who have a 640x480 256-colour mode, but feel
you're missing out by not seeing this 16-colour file selector :-), you
can force zgv to use it by using the \fI--force-fs-16col\fR option.)
.PP
.SH "THE VIEWER"
When a picture is being shown onscreen, you're in the viewer. This
section describes what you can do while viewing the picture.
.PP
.SH "EXITING THE VIEWER"
Exiting the viewer is simple:
.PP
`\fBEsc\fR'
.RS
.RE
`\fBx\fR'
.RS
Exit the viewer.
.PP
If you got to the viewer from the file selector, you're returned there;
if you bypassed the file selector (by running zgv with a file (or files)
to view specified on the command-line --- see \fBOptions\fR) then
exiting the viewer also exits zgv.
.RE
.PP
.SH "BIG PICTURES"
A picture may well be too large to fit entirely on the screen. There are
two general ways to see the whole of the picture, and in addition to
those, you may be able to fit more on by choosing a different video mode
(see \fBVideo Modes\fR), either manually or by using auto-mode-fit.
.PP
(For multi-resolution Photo-CD files, there is yet another alternative
approach (see \fBSupported File Formats\fR).)
.PP
.SS "Scrolling"
Scrolling is the default approach to handling big pictures in zgv. When
the viewer is started up, the top-left of the picture is shown --- you
can use the cursor keys (and many others) to move around the rest of the
picture.
.PP
`\fBCursor Up\fR'
.RS
.RE
`\fBK\fR'
.RS
.RE
`\fBQ\fR'
.RS
Move up 100 pixels. `\fBk\fR' and `\fBq\fR' move up 10 pixels.
.PP
.RE
`\fBCursor Down\fR'
.RS
.RE
`\fBJ\fR'
.RS
.RE
`\fBA\fR'
.RS
Move down 100 pixels. `\fBj\fR' and `\fBa\fR' move down 10 pixels.
.PP
.RE
`\fBCursor Left\fR'
.RS
.RE
`\fBH\fR'
.RS
.RE
`\fBO\fR'
.RS
Move left 100 pixels. `\fBh\fR' and `\fBo\fR' move left 10 pixels.
.PP
.RE
`\fBCursor Right\fR'
.RS
.RE
`\fBL\fR'
.RS
.RE
`\fBP\fR'
.RS
Move right 100 pixels. `\fBl\fR' and `\fBp\fR' move right 10 pixels.
.PP
.RE
`\fBPage Up\fR'
.RS
.RE
`\fB^U\fR'
.RS
Move up (nearly) a screenful. (It moves 90% of the screen height.)
.PP
.RE
`\fBPage Down\fR'
.RS
.RE
`\fB^V\fR'
.RS
Move down (nearly) a screenful.
.PP
.RE
`\fB-\fR'
.RS
Move left (nearly) a screenful. (It moves 90% of the screen width.)
.PP
.RE
`\fB=\fR'
.RS
Move right (nearly) a screenful.
.PP
.RE
`\fBHome\fR'
.RS
.RE
`\fB^A\fR'
.RS
Move to the top-left of the picture.
.PP
.RE
`\fBEnd\fR'
.RS
.RE
`\fB^E\fR'
.RS
Move to the bottom-right of the picture.
.RE
.PP
.SS "Zoom Mode"
An alternative way of viewing the whole picture, one which lets you see
the picture onscreen all at once no matter how big (or small) it is, is
zoom mode.
.PP
Zoom mode's name derives from the idea of `zooming' a small file up to
fit the screen. But in reality, it is more often used to reduce a large
file to fit the screen.
.PP
Zoom mode is not the default, and has to be enabled. Once enabled, it
stays on until you turn it off again.
.PP
By default, the way zoom mode reduces a file to fit the screen is
(relatively) quick but harsh, and may make the picture look ugly.
Enabling \fIvkludge\fR smoothes the picture, giving a better and more
accurate result, but takes longer. It too is not the default, but stays
on until turned off again.
.PP
`\fBz\fR'
.RS
Toggle zoom mode.
.PP
.RE
`\fBAlt-r\fR'
.RS
When in zoom mode, only \fIreduce\fR pictures to fit. This can be
useful when going through a lot of unpredictably-sized pictures, as it
means that you can see all of a big picture easily without also meaning
that tiny little icons assume a scale of Biblical proportions. :-)
.PP
.RE
`\fBv\fR'
.RS
Toggle \fIvkludge\fR, which enables appropriate smoothing when zoom
mode is reducing a picture to fit the screen. It also enables similar
smoothing for non-zoomed pictures in 320x400x8 and 360x480x8 modes.
See \fBVirtual Modes\fR.
.PP
.RE
`\fBn\fR'
.RS
Resume `normal' display --- disables zoom mode (and scaling mode).
.RE
.PP
.SS "Auto-mode-fit"
If it seems strange to you to use scrolling or zoom mode to see the
whole picture when you could just use a different video mode (to change
the size of the pixels displayed onscreen), you may find auto-mode-fit
useful.
.PP
If enabled, and when a picture is loaded, the current mode is
automatically switched to the `smallest' mode which is both wider and
taller than the picture is (or of equal width/height). In other words,
the (theoretically) most appropriate mode. If no mode can fit the
picture onscreen, the `largest' mode is chosen.
.PP
Auto-mode-fit is not the default, so you have to enable it if you want
to use it.
.PP
`\fBZ\fR'
.RS
Toggle auto-mode-fit mode. Usually this only takes effect when a picture
is loaded (so that manual mode switching still works), but when you
enable it zgv does a one-off auto-mode-fit on the current picture. (Note
also that disabling it leaves you in the current mode, so that has no
obvious effect; for this reason, the picture is redrawn (as a visual cue
that you haven't just been ignored :-)).)
.RE
.PP
I should point out that all the mode-switching can be a bit hard on your
monitor, so even if you really like this option you might not want to
enable it all the time (e.g. in a config file), but instead only turn it
on when you `need' it. Still, it's up to you.
.PP
Certain modes are excluded from those chosen by auto-mode-fit. In
particular, no 320x200 mode is ever chosen, nor is 320x400x8. These
exceptions are made due to the unusual aspect ratio. 640x480x4 is
excluded due to the slightly odd way it works, which makes it ill-suited
to automatic selection. 360x480x8 \fIis\fR considered, despite the
aspect ratio, if no 640x480x8 mode exists.
.PP
.SH "SCALING"
You can scale a picture --- this makes it appear larger onscreen. zgv
acts exactly as if the scaled-up picture were the real picture; for
example, the cursors scroll around in steps of 100 scaled-up pixels,
even if this means moving a fraction of a pixel in the original picture.
.PP
The main limitation of scaling is that you can only scale up by integer
values, so you can only make each pixel in the image twice as wide/high, or
three times as wide/high, or four times, and so on.
.PP
(It may seem odd saying e.g. `twice as wide/high' rather than `twice the
size', but technically `twice the size' would be referring to scaling up
the width (and height) by about 1.414...)
.PP
Normally, zgv does no scaling, which could be considered a ratio of 1:1.
Scaling up increases that ratio. How it is increased depends on which
key you use:
.PP
`\fBs\fR'
.RS
Increase the ratio by adding one --- this leads to ratios of 2:1, 3:1,
4:1...
.PP
.RE
`\fBd\fR'
.RS
Increase the ratio by doubling it --- leads to ratios of 2:1, 4:1,
8:1...
.RE
.PP
Usually `\fBd\fR' is more useful.
.PP
There are similar commands to decrease the ratio (when it reaches 1:1
scaling is disabled):
.PP
`\fBS\fR'
.RS
Decrease the ratio by subtracting one.
.PP
.RE
`\fBD\fR'
.RS
Decrease the ratio by halving it.
.RE
.PP
The scaling ratio is never decreased below 1:1. It is also never
increased beyond 512:1, where zgv stops so that pixels may be conserved
for future generations. :-)
.PP
You can undo the effect of scaling at any time by using `\fBn\fR' (which
also disables zoom mode).
.PP
Normally, scaling works by simply making the pixels into larger and
larger squares (in effect), which remain the same colour. However, if
you are using a 15/16/24/32-bit mode (see \fBVideo Modes\fR), you can
enable a feature called `interpolation' which smoothly graduates the
colour change between the top-left corners of each pixel. This is
\fIvery\fR slow, but looks nice.
.PP
`\fBi\fR'
.RS
Toggle interpolation in scaling mode.
.PP
.RE
`\fB!\fR'
.RS
Toggle off-by-one interpolation (disabled by default). Using this
off-by-one method gives incorrect results, but this can occasionally be
useful at ratios of 2:1 and 3:1 for relatively low-quality JPEGs.
.RE
.PP
(If you like the appearance of scaling with interpolation, you may also
be interested in a program I wrote called \fIpnminterp\fR, which can
scale up a PGM or PPM file while applying this effect.)