photo.n

linux系统下的音频通信

Specifies that the source region should be magnified by a factor of
\fIx\fR in the X direction and \fIy\fR in the Y direction.  If \fIy\fR
is not given, the default value is the same as \fIx\fR.  With this
option, each pixel in the source image will be expanded into a block
of \fIx\fR x \fIy\fR pixels in the destination image, all the same
color.  \fIx\fR and \fIy\fR must be greater than 0.
.TP
\fB\-subsample \fIx y\fR
Specifies that the source image should be reduced in size by using
only every \fIx\fRth pixel in the X direction and \fIy\fRth pixel in
the Y direction.  Negative values will cause the image to be flipped
about the Y or X axes, respectively.  If \fIy\fR is not given, the
default value is the same as \fIx\fR.
.RE
.TP
\fIimageName \fBget\fR \fIx y\fR
Returns the color of the pixel at coordinates (\fIx\fR,\fIy\fR) in the
image as a list of three integers between 0 and 255, representing the
red, green and blue components respectively.
.TP
\fIimageName \fBput \fIdata\fR ?\fB\-to\fI x1 y1 x2 y2\fR?
Sets pixels in \fIimageName\fR to the colors specified in \fIdata\fR.
\fIdata\fR is used to form a two-dimensional array of pixels that are
then copied into the \fIimageName\fR.  \fIdata\fR is structured as a
list of horizontal rows, from top to bottom, each of which is a list
of colors, listed from left to right.  Each color may be specified by name
(e.g., blue) or in hexadecimal form (e.g., #2376af).  The
\fB\-to\fR option can be used to specify the area of \fIimageName\fR to be
affected.  If only \fIx1\fR and \fIy1\fR are given, the area affected
has its top-left corner at (\fIx1,y1\fR) and is the same size as the
array given in \fIdata\fR.  If all four coordinates are given, they
specify diagonally opposite corners of the affected rectangle, and the
array given in \fIdata\fR will be replicated as necessary in the X and
Y directions to fill the rectangle.
.TP
\fIimageName \fBread\fR \fIfilename\fR ?\fIoption value(s) ...\fR?
Reads image data from the file named \fIfilename\fR into the image.
This command first searches the list of
image file format handlers for a handler that can interpret the data
in \fIfilename\fR, and then reads the image in \fIfilename\fR into
\fIimageName\fR (the destination image).  The following options may be
specified:
.RS
.TP
\fB\-format \fIformat-name\fR
Specifies the format of the image data in \fIfilename\fR.
Specifically, only image file format handlers whose names begin with
\fIformat-name\fR will be used while searching for an image data
format handler to read the data.
.TP
\fB\-from \fIx1 y1 x2 y2\fR
Specifies a rectangular sub-region of the image file data to be copied
to the destination image.  If only \fIx1\fR and \fIy1\fR are
specified, the region extends from (\fIx1,y1\fR) to the bottom-right
corner of the image in the image file.  If all four coordinates are
specified, they specify diagonally opposite corners or the region.
The default, if this option is not specified, is the whole of the
image in the image file.
.TP
\fB\-shrink\fR
If this option, the size of \fIimageName\fR will be reduced, if
necessary, so that the region into which the image file data are read
is at the bottom-right corner of the \fIimageName\fR.  This option
will not affect the width or height of the image if the user has
specified a non-zero value for the \fB\-width\fR or \fB\-height\fR
configuration option, respectively.
.TP
\fB\-to \fIx y\fR
Specifies the coordinates of the top-left corner of the region of
\fIimageName\fR into which data from \fIfilename\fR are to be read.
The default is (0,0).
.RE
.TP
\fIimageName \fBredither\fR
The dithering algorithm used in displaying photo images propagates
quantization errors from one pixel to its neighbors.
If the image data for \fIimageName\fR is supplied in pieces, the
dithered image may not be exactly correct.  Normally the difference is
not noticeable, but if it is a problem, this command can be used to
recalculate the dithered image in each window where the image is
displayed.
.TP
\fIimageName \fBwrite \fIfilename\fR ?\fIoption value(s) ...\fR?
Writes image data from \fIimageName\fR to a file named \fIfilename\fR.
The following options may be specified:
.RS
.TP
\fB\-format\fI format-name\fR
Specifies the name of the image file format handler to be used to
write the data to the file.  Specifically, this subcommand searches
for the first handler whose name matches a initial substring of
\fIformat-name\fR and which has the capability to write an image
file.  If this option is not given, this subcommand uses the first
handler that has the capability to write an image file.
.TP
\fB\-from \fIx1 y1 x2 y2\fR
Specifies a rectangular region of \fIimageName\fR to be written to the
image file.  If only \fIx1\fR and \fIy1\fR are specified, the region
extends from \fI(x1,y1)\fR to the bottom-right corner of
\fIimageName\fR.  If all four coordinates are given, they specify
diagonally opposite corners of the rectangular region.  The default,
if this option is not given, is the whole image.
.RE
.SH "IMAGE FORMATS"
.PP
The photo image code is structured to allow handlers for additional
image file formats to be added easily.  The photo image code maintains
a list of these handlers.  Handlers are added to the list by
registering them with a call to \fBTk_CreatePhotoImageFormat\fR.  The
standard Tk distribution comes with handlers for PPM/PGM and GIF formats,
which are automatically registered on initialization.
.PP
When reading an image file or processing
string data specified with the \fB\-data\fR configuration option, the
photo image code invokes each handler in turn until one is
found that claims to be able to read the data in the file or string.
Usually this will find the correct handler, but if it doesn't, the
user may give a format name with the \fB\-format\fR option to specify
which handler to use.  In fact the photo image code will try those
handlers whose names begin with the string specified for the
\fB\-format\fR option (the comparison is case-insensitive).  For
example, if the user specifies \fB\-format gif\fR, then a handler
named GIF87 or GIF89 may be invoked, but a handler
named JPEG may not (assuming that such handlers had been
registered).
.PP
When writing image data to a file, the processing of the
\fB\-format\fR option is slightly different: the string value given
for the \fB\-format\fR option must begin with the complete name of the
requested handler, and may contain additional information following
that, which the handler can use, for example, to specify which variant
to use of the formats supported by the handler.

.SH "COLOR ALLOCATION"
.PP
When a photo image is displayed in a window, the photo image code
allocates colors to use to display the image and dithers the image, if
necessary, to display a reasonable approximation to the image using
the colors that are available.  The colors are allocated as a color
cube, that is, the number of colors allocated is the product of the
number of shades of red, green and blue.
.PP
Normally, the number of
colors allocated is chosen based on the depth of the window.  For
example, in an 8-bit PseudoColor window, the photo image code will
attempt to allocate seven shades of red, seven shades of green and
four shades of blue, for a total of 198 colors.  In a 1-bit StaticGray
(monochrome) window, it will allocate two colors, black and white.  In
a 24-bit DirectColor or TrueColor window, it will allocate 256 shades
each of red, green and blue.  Fortunately, because of the way that
pixel values can be combined in DirectColor and TrueColor windows,
this only requires 256 colors to be allocated.  If not all of the
colors can be allocated, the photo image code reduces the number of
shades of each primary color and tries again.
.PP
The user can exercise some control over the number of colors that a
photo image uses with the \fB\-palette\fR configuration option.  If
this option is used, it specifies the maximum number of shades of
each primary color to try to allocate.  It can also be used to force
the image to be displayed in shades of gray, even on a color display,
by giving a single number rather than three numbers separated by
slashes.

.SH CREDITS
.PP
The photo image type was designed and implemented by Paul Mackerras,
based on his earlier photo widget and some suggestions from
John Ousterhout.

.SH KEYWORDS
photo, image, color