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IRIX Base Documentation 1998 November
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IRIX 6.5.2 Base Documentation November 1998.img
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catman
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Tk
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photo.z
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photo
Wrap
Text File
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1998-10-30
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23KB
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463 lines
pppphhhhoooottttoooo((((3333TTTTkkkk)))) pppphhhhoooottttoooo((((3333TTTTkkkk))))
NNNNAAAAMMMMEEEE
photo - Full-color images
SSSSYYYYNNNNOOOOPPPPSSSSIIIISSSS
iiiimmmmaaaaggggeeee ccccrrrreeeeaaaatttteeee pppphhhhoooottttoooo ?_n_a_m_e? ?_o_p_t_i_o_n_s?
DDDDEEEESSSSCCCCRRRRIIIIPPPPTTTTIIIIOOOONNNN
A photo is an image whose pixels can display any color or be transparent.
A photo image is stored internally in full color (24 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 PPM/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.
CCCCRRRREEEEAAAATTTTIIIINNNNGGGG PPPPHHHHOOOOTTTTOOOOSSSS
Like all images, photos are created using the iiiimmmmaaaaggggeeee ccccrrrreeeeaaaatttteeee command.
Photos support the following _o_p_t_i_o_n_s:
----ddddaaaattttaaaa _s_t_r_i_n_g
Specifies the contents of the image as a string. 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 ----ddddaaaattttaaaa and ----ffffiiiilllleeee
options are specified, the ----ffffiiiilllleeee option takes precedence.
----ffffoooorrrrmmmmaaaatttt _f_o_r_m_a_t-_n_a_m_e
Specifies the name of the file format for the data specified with
the ----ddddaaaattttaaaa or ----ffffiiiilllleeee option.
----ffffiiiilllleeee _n_a_m_e
_n_a_m_e 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 from a
file.
----ggggaaaammmmmmmmaaaa _v_a_l_u_e
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 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.
----hhhheeeeiiiigggghhhhtttt _n_u_m_b_e_r
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)
PPPPaaaaggggeeee 1111
pppphhhhoooottttoooo((((3333TTTTkkkk)))) pppphhhhoooottttoooo((((3333TTTTkkkk))))
allows the image to expand or shrink vertically to fit the data
stored in it.
----ppppaaaalllleeeetttttttteeee _p_a_l_e_t_t_e-_s_p_e_c
Specifies the resolution of the color cube to be allocated for
displaying this image, and thus the number of colors used from the
colormaps of the windows where it is displayed. The _p_a_l_e_t_t_e-_s_p_e_c
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).
----wwwwiiiiddddtttthhhh _n_u_m_b_e_r
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.
IIIIMMMMAAAAGGGGEEEE CCCCOOOOMMMMMMMMAAAANNNNDDDD
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:
_i_m_a_g_e_N_a_m_e _o_p_t_i_o_n ?_a_r_g _a_r_g ...?
_O_p_t_i_o_n and the _a_r_gs determine the exact behavior of the command.
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 ----wwwwiiiiddddtttthhhh and/or
----hhhheeeeiiiigggghhhhtttt configuration options, in which case the width and/or height,
respectively, of the image will not be changed.
The following commands are possible for photo images:
_i_m_a_g_e_N_a_m_e bbbbllllaaaannnnkkkk
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.
_i_m_a_g_e_N_a_m_e ccccggggeeeetttt _o_p_t_i_o_n
Returns the current value of the configuration option given by
_o_p_t_i_o_n. _O_p_t_i_o_n may have any of the values accepted by the iiiimmmmaaaaggggeeee
ccccrrrreeeeaaaatttteeee pppphhhhoooottttoooo command.
_i_m_a_g_e_N_a_m_e ccccoooonnnnffffiiiigggguuuurrrreeee ?_o_p_t_i_o_n? ?_v_a_l_u_e _o_p_t_i_o_n _v_a_l_u_e ...?
Query or modify the configuration options for the image. If no
_o_p_t_i_o_n is specified, returns a list describing all of the available
options for _i_m_a_g_e_N_a_m_e (see TTTTkkkk____CCCCoooonnnnffffiiiigggguuuurrrreeeeIIIInnnnffffoooo for information on the
PPPPaaaaggggeeee 2222
pppphhhhoooottttoooo((((3333TTTTkkkk)))) pppphhhhoooottttoooo((((3333TTTTkkkk))))
format of this list). If _o_p_t_i_o_n is specified with no _v_a_l_u_e, then
the command returns a list describing the one named option (this
list will be identical to the corresponding sublist of the value
returned if no _o_p_t_i_o_n is specified). If one or more _o_p_t_i_o_n-_v_a_l_u_e
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. _O_p_t_i_o_n may have any of the values accepted by the
iiiimmmmaaaaggggeeee ccccrrrreeeeaaaatttteeee pppphhhhoooottttoooo command.
_i_m_a_g_e_N_a_m_e ccccooooppppyyyy _s_o_u_r_c_e_I_m_a_g_e ?_o_p_t_i_o_n _v_a_l_u_e(_s) ...?
Copies a region from the image called _s_o_u_r_c_e_I_m_a_g_e (which must be a
photo image) to the image called _i_m_a_g_e_N_a_m_e, possibly with pixel
zooming and/or subsampling. If no options are specified, this
command copies the whole of _s_o_u_r_c_e_I_m_a_g_e into _i_m_a_g_e_N_a_m_e, starting at
coordinates (0,0) in _i_m_a_g_e_N_a_m_e. The following options may be
specified:
----ffffrrrroooommmm _x_1 _y_1 _x_2 _y_2
Specifies a rectangular sub-region of the source image to be
copied. (_x_1,_y_1) and (_x_2,_y_2) specify diagonally opposite
corners of the rectangle. If _x_2 and _y_2 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
----ffffrrrroooommmm option is not given, the default is the whole source
image.
----ttttoooo _x_1 _y_1 _x_2 _y_2
Specifies a rectangular sub-region of the destination image to
be affected. (_x_1,_y_1) and (_x_2,_y_2) specify diagonally opposite
corners of the rectangle. If _x_2 and _y_2 are not specified, the
default value is (_x_1,_y_1) plus the size of the source region
(after subsampling and zooming, if specified). If _x_2 and _y_2
are specified, the source region will be replicated if
necessary to fill the destination region in a tiled fashion.
----sssshhhhrrrriiiinnnnkkkk
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 ----wwwwiiiiddddtttthhhh or ----hhhheeeeiiiigggghhhhtttt
configuration option, respectively.
----zzzzoooooooommmm _x _y
Specifies that the source region should be magnified 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.
PPPPaaaaggggeeee 3333
pppphhhhoooottttoooo((((3333TTTTkkkk)))) pppphhhhoooottttoooo((((3333TTTTkkkk))))
----ssssuuuubbbbssssaaaammmmpppplllleeee _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. Negative 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.
_i_m_a_g_e_N_a_m_e ggggeeeetttt _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.
_i_m_a_g_e_N_a_m_e ppppuuuutttt _d_a_t_a ?----ttttoooo _x_1 _y_1 _x_2 _y_2?
Sets pixels in _i_m_a_g_e_N_a_m_e to the colors specified in _d_a_t_a. _d_a_t_a is
used to form a two-dimensional array of pixels that are then copied
into the _i_m_a_g_e_N_a_m_e. _d_a_t_a 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 ----ttttoooo option can be
used to specify the area of _i_m_a_g_e_N_a_m_e to be affected. If only _x_1
and _y_1 are given, the area affected has its top-left corner at
(_x_1,_y_1) and is the same size as the array given in _d_a_t_a. If all
four coordinates are given, they specify diagonally opposite corners
of the affected rectangle, and the array given in _d_a_t_a will be
replicated as necessary in the X and Y directions to fill the
rectangle.
_i_m_a_g_e_N_a_m_e rrrreeeeaaaadddd _f_i_l_e_n_a_m_e ?_o_p_t_i_o_n _v_a_l_u_e(_s) ...?
Reads image data from the file named _f_i_l_e_n_a_m_e into the image. This
command first searches the list of image file format handlers for a
handler that can interpret the data in _f_i_l_e_n_a_m_e, and then reads the
image in _f_i_l_e_n_a_m_e into _i_m_a_g_e_N_a_m_e (the destination image). The
following options may be specified:
----ffffoooorrrrmmmmaaaatttt _f_o_r_m_a_t-_n_a_m_e
Specifies the format of the image data in _f_i_l_e_n_a_m_e.
Specifically, only image file format handlers whose names begin
with _f_o_r_m_a_t-_n_a_m_e will be used while searching for an image data
format handler to read the data.
----ffffrrrroooommmm _x_1 _y_1 _x_2 _y_2
Specifies a rectangular sub-region of the image file data to be
copied to the destination image. If only _x_1 and _y_1 are
specified, the region extends from (_x_1,_y_1) 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.
----sssshhhhrrrriiiinnnnkkkk
If this option, the size of _i_m_a_g_e_N_a_m_e will be reduced, if
necessary, so that the region into which the image file data
PPPPaaaaggggeeee 4444
pppphhhhoooottttoooo((((3333TTTTkkkk)))) pppphhhhoooottttoooo((((3333TTTTkkkk))))
are read is at the bottom-right corner of the _i_m_a_g_e_N_a_m_e. This
option will not affect the width or height of the image if the
user has specified a non-zero value for the ----wwwwiiiiddddtttthhhh or ----hhhheeeeiiiigggghhhhtttt
configuration option, respectively.
----ttttoooo _x _y
Specifies the coordinates of the top-left corner of the region
of _i_m_a_g_e_N_a_m_e into which data from _f_i_l_e_n_a_m_e are to be read. The
default is (0,0).
_i_m_a_g_e_N_a_m_e rrrreeeeddddiiiitttthhhheeeerrrr
The dithering algorithm used in displaying photo images propagates
quantization errors from one pixel to its neighbors. If the image
data for _i_m_a_g_e_N_a_m_e 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.
_i_m_a_g_e_N_a_m_e wwwwrrrriiiitttteeee _f_i_l_e_n_a_m_e ?_o_p_t_i_o_n _v_a_l_u_e(_s) ...?
Writes image data from _i_m_a_g_e_N_a_m_e to a file named _f_i_l_e_n_a_m_e. The
following options may be specified:
----ffffoooorrrrmmmmaaaatttt _f_o_r_m_a_t-_n_a_m_e
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 _f_o_r_m_a_t-_n_a_m_e 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.
----ffffrrrroooommmm _x_1 _y_1 _x_2 _y_2
Specifies a rectangular region of _i_m_a_g_e_N_a_m_e to be written to
the image file. If only _x_1 and _y_1 are specified, the region
extends from (_x_1,_y_1) to the bottom-right corner of _i_m_a_g_e_N_a_m_e.
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.
IIIIMMMMAAAAGGGGEEEE FFFFOOOORRRRMMMMAAAATTTTSSSS
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 TTTTkkkk____CCCCrrrreeeeaaaatttteeeePPPPhhhhoooottttooooIIIImmmmaaaaggggeeeeFFFFoooorrrrmmmmaaaatttt. The standard Tk distribution
comes with handlers for PPM/PGM and GIF formats, which are automatically
registered on initialization.
When reading an image file or processing string data specified with the
----ddddaaaattttaaaa 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 ----ffffoooorrrrmmmmaaaatttt option to
PPPPaaaaggggeeee 5555
pppphhhhoooottttoooo((((3333TTTTkkkk)))) pppphhhhoooottttoooo((((3333TTTTkkkk))))
specify which handler to use. In fact the photo image code will try
those handlers whose names begin with the string specified for the
----ffffoooorrrrmmmmaaaatttt option (the comparison is case-insensitive). For example, if the
user specifies ----ffffoooorrrrmmmmaaaatttt ggggiiiiffff, 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 ----ffffoooorrrrmmmmaaaatttt option
is slightly different: the string value given for the ----ffffoooorrrrmmmmaaaatttt 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.
CCCCOOOOLLLLOOOORRRR AAAALLLLLLLLOOOOCCCCAAAATTTTIIIIOOOONNNN
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.
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.
The user can exercise some control over the number of colors that a photo
image uses with the ----ppppaaaalllleeeetttttttteeee 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.
CCCCRRRREEEEDDDDIIIITTTTSSSS
The photo image type was designed and implemented by Paul Mackerras,
based on his earlier photo widget and some suggestions from John
Ousterhout.
PPPPaaaaggggeeee 6666
pppphhhhoooottttoooo((((3333TTTTkkkk)))) pppphhhhoooottttoooo((((3333TTTTkkkk))))
KEYWORDS
photo, image, color
PPPPaaaaggggeeee 7777