Tk Built-In Commands photo(1T)
NAME
photo - Full-color images
SYNOPSIS
image create photo ?name? ?options?
DESCRIPTION
A photo is an image whose pixels can display any color or be
transparent. A photo image is stored internally in full
color (32 bits per pixel), and is displayed using dithering
if necessary. Image data for a photo image can be obtained
from a file or a string, or it can be supplied from C code
through a procedural interface. At present, only GIF and
PM/PGM formats are supported, but an interface exists to
allow additional image file formats to be added easily. A
photo image is transparent in regions where no image data
has been supplied or where it has been set transparent by
the transparency set subcommand.
CREATING PHOTOS
Like all images, photos are created using the image create
command. Photos support the following options:
-data string
Specifies the contents of the image as a string. The
string should contain binary data or, for some formats,
base64-encoded data (this is currently guaranteed to be
supported for GIF images). The format of the string
must be one of those for which there is an image file
format handler that will accept string data. If both
the -data and -file options are specified, the -file
option takes precedence.
-format format-name
Specifies the name of the file format for the data
specified with the -data or -file option.
-file name
name gives the name of a file that is to be read to
supply data for the photo image. The file format must
be one of those for which there is an image file format
handler that can read data.
-gamma value
Specifies that the colors allocated for displaying this
image in a window should be corrected for a non-linear
display with the specified gamma exponent value. (The
intensity produced by most CRT displays is a power
Tk Last change: 4.0 1
Tk Built-In Commands photo(1T)
function of the input value, to a good approximation;
gamma is the exponent and is typically around 2). The
value specified must be greater than zero. The default
value is one (no correction). In general, values
greater than one will make the image lighter, and
values less than one will make it darker.
-height number
Specifies the height of the image, in pixels. This
option is useful primarily in situations where the user
wishes to build up the contents of the image piece by
piece. A value of zero (the default) allows the image
to expand or shrink vertically to fit the data stored
in it.
-palette palette-spec
Specifies the resolution of the color cube to be allo-
cated for displaying this image, and thus the number of
colors used from the colormaps of the windows where it
is displayed. The palette-spec string may be either a
single decimal number, specifying the number of shades
of gray to use, or three decimal numbers separated by
slashes (/), specifying the number of shades of red,
green and blue to use, respectively. If the first form
(a single number) is used, the image will be displayed
in monochrome (i.e., grayscale).
-width number
Specifies the width of the image, in pixels. This
option is useful primarily in situations where the user
wishes to build up the contents of the image piece by
piece. A value of zero (the default) allows the image
to expand or shrink horizontally to fit the data stored
in it.
IMAGE COMAND
When a photo image is created, Tk also creates a new command
whose name is the same as the image. This command may be
used to invoke various operations on the image. It has the
following general form:
imageName option ?arg arg ...?
Option and the args determine the exact behavior of the com-
mand.
Those options that write data to the image generally expand
the size of the image, if necessary, to accommodate the data
written to the image, unless the user has specified non-zero
values for the -width and/or -height configuration options,
in which case the width and/or height, respectively, of the
image will not be changed.
Tk Last change: 4.0 2
Tk Built-In Commands photo(1T)
The following commands are possible for photo images:
imageName blank
Blank the image; that is, set the entire image to have
no data, so it will be displayed as transparent, and
the background of whatever window it is displayed in
will show through.
imageName cget option
Returns the current value of the configuration option
given by option. Option may have any of the values
accepted by the image create photo command.
imageName configure ?option? ?value option value ...?
Query or modify the configuration options for the
image. If no option is specified, returns a list
describing all of the available options for imageName
(see TkConfigureInfo for information on the format of
this list). If option is specified with no value, then
the command returns a list describing the one named
option (this list will be identical to the correspond-
ing sublist of the value returned if no option is
specified). If one or more option-value pairs are
specified, then the command modifies the given
option(s) to have the given value(s); in this case the
command returns an empty string. Option may have any
of the values accepted by the image create photo com-
mand.
imageName copy sourceImage ?option value(s) ...?
Copies a region from the image called sourceImage
(which must be a photo image) to the image called
imageName, possibly with pixel zooming and/or subsam-
pling. If no options are specified, this command
copies the whole of sourceImage into imageName, start-
ing at coordinates (0,0) in imageName. The following
options may be specified:
-from x1 y1 x2 y2
Specifies a rectangular sub-region of the source
image to be copied. (x1,y1) and (x2,y2) specify
diagonally opposite corners of the rectangle. If
x2 and y2 are not specified, the default value is
the bottom-right corner of the source image. The
pixels copied will include the left and top edges
of the specified rectangle but not the bottom or
right edges. If the -from option is not given,
the default is the whole source image.
-to x1 y1 x2 y2
Specifies a rectangular sub-region of the destina-
tion image to be affected. (x1,y1) and (x2,y2)
Tk Last change: 4.0 3
Tk Built-In Commands photo(1T)
specify diagonally opposite corners of the rectan-
gle. If x2 and y2 are not specified, the default
value is (x1,y1) plus the size of the source
region (after subsampling and zooming, if speci-
fied). If x2 and y2 are specified, the source
region will be replicated if necessary to fill the
destination region in a tiled fashion.
-shrink
Specifies that the size of the destination image
should be reduced, if necessary, so that the
region being copied into is at the bottom-right
corner of the image. This option will not affect
the width or height of the image if the user has
specified a non-zero value for the -width or
-height configuration option, respectively.
-zoom x y
Specifies that the source region should be magni-
fied by a factor of x in the X direction and y in
the Y direction. If y is not given, the default
value is the same as x. With this option, each
pixel in the source image will be expanded into a
block of x x y pixels in the destination image,
all the same color. x and y must be greater than
0.
-subsample x y
Specifies that the source image should be reduced
in size by using only every xth pixel in the X
direction and yth pixel in the Y direction. Nega-
tive values will cause the image to be flipped
about the Y or X axes, respectively. If y is not
given, the default value is the same as x.
-compositingrule rule
Specifies how transparent pixels in the source
image are combined with the destination image.
When a compositing rule of overlay is set, the old
contents of the destination image are visible, as
if the source image were printed on a piece of
transparent film and placed over the top of the
destination. When a compositing rule of set is
set, the old contents of the destination image are
discarded and the source image is used as-is. The
default compositing rule is overlay.
imageName data ?option value(s) ...?
Returns image data in the form of a string. The follow-
ing options may be specified:
-background color
Tk Last change: 4.0 4
Tk Built-In Commands photo(1T)
If the color is specified, the data will not con-
tain any transparency information. In all tran-
sparent pixels the color will be replaced by the
specified color.
-format format-name
Specifies the name of the image file format
handler to be used. Specifically, this subcommand
searches for the first handler whose name matches
an initial substring of format-name and which has
the capability to read this image data. If this
option is not given, this subcommand uses the
first handler that has the capability to read the
image data.
-from x1 y1 x2 y2
Specifies a rectangular region of imageName to be
returned. If only x1 and y1 are specified, the
region extends from (x1,y1) to the bottom-right
corner of imageName. If all four coordinates are
given, they specify diagonally opposite corners of
the rectangular region, including x1,y1 and
excluding x2,y2. The default, if this option is
not given, is the whole image.
-grayscale
If this options is specified, the data will not
contain color information. All pixel data will be
transformed into grayscale.
imageName get x y
Returns the color of the pixel at coordinates (x,y) in
the image as a list of three integers between 0 and
255, representing the red, green and blue components
respectively.
imageName put data ?option value(s) ...?
Sets pixels in imageName to the data specified in
data. This command first searches the list of image
file format handlers for a handler that can interpret
the data in data, and then reads the image encoded
within into imageName (the destination image). If data
does not match any known format, an attempt to inter-
pret it as a (top-to-bottom) list of scan-lines is
made, with each scan-line being a (left-to-right) list
of pixel colors (see TkGetColor for a description of
valid colors.) Every scan-line must be of the same
length. Note that when data is a single color name,
you are instructing Tk to fill a rectangular region
with that color. The following options may be speci-
fied:
Tk Last change: 4.0 5
Tk Built-In Commands photo(1T)
-format format-name
Specifies the format of the image data in data.
Specifically, only image file format handlers
whose names begin with format-name will be used
while searching for an image data format handler
to read the data.
-to x1 y1 ?x2 y2?
Specifies the coordinates of the top-left corner
(x1,y1) of the region of imageName into which data
from filename are to be read. The default is
(0,0). If x2,y2 is given and data is not large
enough to cover the rectangle specified by this
option, the image data extracted will be tiled so
it covers the entire destination rectangle. Note
that if data specifies a single color value, then
a region extending to the bottom-right corner
represented by (x2,y2) will be filled with that
color.
imageName read filename ?option value(s) ...?
Reads image data from the file named filename into the
image. This command first searches the list of image
file format handlers for a handler that can interpret
the data in filename, and then reads the image in
filename into imageName (the destination image). The
following options may be specified:
-format format-name
Specifies the format of the image data in
filename. Specifically, only image file format
handlers whose names begin with format-name will
be used while searching for an image data format
handler to read the data.
-from x1 y1 x2 y2
Specifies a rectangular sub-region of the image
file data to be copied to the destination image.
If only x1 and y1 are specified, the region
extends from (x1,y1) to the bottom-right corner of
the image in the image file. If all four coordi-
nates are specified, they specify diagonally oppo-
site corners or the region. The default, if this
option is not specified, is the whole of the image
in the image file.
-shrink
If this option, the size of imageName 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 imageName. This option
will not affect the width or height of the image
Tk Last change: 4.0 6
Tk Built-In Commands photo(1T)
if the user has specified a non-zero value for the
-width or -height configuration option, respec-
tively.
-to x y
Specifies the coordinates of the top-left corner
of the region of imageName into which data from
filename are to be read. The default is (0,0).
imageName redither
The dithering algorithm used in displaying photo images
propagates quantization errors from one pixel to its
neighbors. If the image data for imageName 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.
imageName transparency subcommand ?arg arg ...?
Allows examination and manipulation of the transparency
information in the photo image. Several subcommands
are available:
imageName transparency get x y
Returns a boolean indicating if the pixel at (x,y)
is transparent.
imageName transparency set x y boolean
Makes the pixel at (x,y) transparent if boolean is
true, and makes that pixel opaque otherwise.
imageName write filename ?option value(s) ...?
Writes image data from imageName to a file named
filename. The following options may be specified:
-background color
If the color is specified, the data will not con-
tain any transparency information. In all tran-
sparent pixels the color will be replaced by the
specified color.
-format format-name
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 an initial sub-
string of format-name 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.
Tk Last change: 4.0 7
Tk Built-In Commands photo(1T)
-from x1 y1 x2 y2
Specifies a rectangular region of imageName to be
written to the image file. If only x1 and y1 are
specified, the region extends from (x1,y1) to the
bottom-right corner of imageName. 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.
-grayscale
If this options is specified, the data will not
contain color information. All pixel data will be
transformed into grayscale.
IMAGE FORMATS
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
TkCreatePhotoImageFormat. The standard Tk distribution
comes with handlers for PM/PGM and GIF formats, which are
automatically registered on initialization.
When reading an image file or processing string data speci-
fied with the -data 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 -format
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 -format option (the comparison
is case-insensitive). For example, if the user specifies
-format gif, then a handler named GIF87 or GIF89 may be
invoked, but a handler named JPEG may not (assuming that
such handlers had been registered).
When writing image data to a file, the processing of the
-format option is slightly different: the string value given
for the -format option must begin with the complete name of
the requested handler, and may contain additional informa-
tion following that, which the handler can use, for example,
to specify which variant to use of the formats supported by
the handler. Note that not all image handlers may support
writing transparency data to a file, even where the target
image format does.
COLOR ALOCATION
When a photo image is displayed in a window, the photo image
code allocates colors to use to display the image and dith-
ers the image, if necessary, to display a reasonable
Tk Last change: 4.0 8
Tk Built-In Commands photo(1T)
approximation to the image using the colors that are avail-
able. 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.
Normally, the number of colors allocated is chosen based on
the depth of the window. For example, in an 8-bit Pseu-
doColor window, the photo image code will attempt to allo-
cate seven shades of red, seven shades of green and four
shades of blue, for a total of 198 colors. In a 1-bit Sta-
ticGray (monochrome) window, it will allocate two colors,
black and white. In a 24-bit DirectColor or TrueColor win-
dow, 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.
The user can exercise some control over the number of colors
that a photo image uses with the -palette 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.
CREDITS
The photo image type was designed and implemented by Paul
Mackerras, based on his earlier photo widget and some
suggestions from John Ousterhout.
EXAMPLE
Load an image from a file and tile it to the size of a win-
dow, which is useful for producing a tiled background:
# These lines should be called once
image create photo untiled -file "theFile.ppm"
image create photo tiled
# These lines should be called whenever .someWidget changes
# size; a binding is useful here
set width [winfo width .someWidget]
set height [winfo height .someWidget]
tiled copy untiled -to 0 0 $width $height -shrink
SEE ALSO
image(1T)
KEYWORDS
photo, image, color
Tk Last change: 4.0 9
Tk Built-In Commands photo(1T)
ATRIBUTES
See attributes(5) for descriptions of the following attri-
butes:
ATRIBUTE TYPE ATRIBUTE VALUE
Availability SUNWTk
Interface Stability Uncommitted
NOTES
Source for Tk is available on http:/opensolaris.org.
Tk Last change: 4.0 10
|
