Manual Pages for UNIX Darwin command on man photo

photo(n) Tk Built-In Commands photo(n)

NAME

photo - Full-color images

SYNOPSIS

iimmaaggee ccrreeaattee pphhoottoo ?name? ?options?

DESCRIPTION

A photo is an image whose pixels can display any color or be transpar-

ent. 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 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 or where | it has been set transparent by the ttrraannssppaarreennccyy sseett subcommand. CCRREEAATTIINNGG PPHHOOTTOOSS

Like all images, photos are created using the iimmaaggee ccrreeaattee command.

Photos support the following options:

-ddaattaa string

Specifies the contents of the image as a string. The string can contain base64 encoded data or binary data. 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 -ddaattaa

and -ffiillee options are specified, the -ffiillee option takes prece-

dence.

-ffoorrmmaatt format-name

Specifies the name of the file format for the data specified

with the -ddaattaa or -ffiillee option.

-ffiillee 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.

-ggaammmmaa 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 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.

-hheeiigghhtt 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.

-ppaalleettttee palette-spec

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

palette-spec string may be either a single decimal number, spec-

ifying 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 dis-

played in monochrome (i.e., grayscale).

-wwiiddtthh 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. IIMMAAGGEE CCOOMMMMAANNDD

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 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 -wwiiddtthh and/or

-hheeiigghhtt 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:

imageName bbllaannkk 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 ccggeett option Returns the current value of the configuration option given by option. Option may have any of the values accepted by the iimmaaggee ccrreeaattee pphhoottoo command. imageName ccoonnffiigguurree ?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 avail-

able options for imageName (see TTkkCCoonnffiigguurreeIInnffoo 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 corresponding 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 iimmaaggee ccrreeaattee pphhoottoo command. imageName ccooppyy 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 subsampling. If no options are specified, this command copies the whole of sourceImage into imageName, starting at coordinates (0,0) in imageName. The following options may be specified:

-ffrroomm x1 y1 x2 y2

Specifies a rectangular sub-region of the source image to

be copied. (x1,y1) and (x2,y2) specify diagonally oppo-

site 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 -ffrroomm option is not given,

the default is the whole source image.

-ttoo x1 y1 x2 y2

Specifies a rectangular sub-region of the destination

image to be affected. (x1,y1) and (x2,y2) specify diago-

nally opposite corners of the rectangle. 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 specified). If x2 and y2 are specified, the source

region will be replicated if necessary to fill the desti-

nation region in a tiled fashion.

-sshhrriinnkk

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 -wwiiddtthh

or -hheeiigghhtt configuration option, respectively.

-zzoooomm 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.

-ssuubbssaammppllee 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.

-ccoommppoossiittiinnggrruullee 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 destina- |

tion 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 ddaattaa ??option value(s) ...? Returns image data in the form of a string. The following options may be specified:

-bbaacckkggrroouunndd color

If the color is specified, the data will not contain any transparency information. In all transparent pixels the color will be replaced by the specified color.

-ffoorrmmaatt 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 a 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.

-ffrroomm 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 image-

Name. 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.

-ggrraayyssccaallee

If this options is specified, the data will not contain color information. All pixel data will be transformed into grayscale. imageName ggeett 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 ppuutt 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

interpret 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 TTkkGGeettCCoolloorr 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 specified:

-ffoorrmmaatt format-name

Specifies the format of the image data in data. Specifi-

cally, 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.

-ttoo 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 spec-

ified 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 rreeaadd 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 han-

dlers 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:

-ffoorrmmaatt 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.

-ffrroomm 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 coordinates are specified, they specify diago-

nally opposite corners or the region. The default, if this option is not specified, is the whole of the image in the image file.

-sshhrriinnkk

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 image-

Name. This option will not affect the width or height of

the image if the user has specified a non-zero value for

the -wwiiddtthh or -hheeiigghhtt configuration option, respectively.

-ttoo 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 rreeddiitthheerr

The dithering algorithm used in displaying photo images propa-

gates 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 ttrraannssppaarreennccyy subcommand ?arg arg ...?

Allows examination and manipulation of the transparency informa- |

tion in the photo image. Several subcommands are available: |

imageName ttrraannssppaarreennccyy ggeett x | y | | Returns a boolean indicating if the pixel at (x,y) is | transparent. | imageName ttrraannssppaarreennccyy sseett x y | boolean | | Makes the pixel at (x,y) transparent if boolean is true, | and makes that pixel opaque otherwise. | imageName wwrriittee filename ?option value(s) ...? Writes image data from imageName to a file named filename. The following options may be specified:

-bbaacckkggrroouunndd color

If the color is specified, the data will not contain any transparency information. In all transparent pixels the color will be replaced by the specified color.

-ffoorrmmaatt 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 a initial substring 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.

-ffrroomm 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 spec-

ify diagonally opposite corners of the rectangular region. The default, if this option is not given, is the whole image.

-ggrraayyssccaallee

If this options is specified, the data will not contain color information. All pixel data will be transformed into grayscale. IIMMAAGGEE FFOORRMMAATTSS

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 register-

ing them with a call to TTkkCCrreeaatteePPhhoottooIImmaaggeeFFoorrmmaatt. 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

-ddaattaa 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 -ffoorrmmaatt 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

-ffoorrmmaatt option (the comparison is case-insensitive). For example, if

the user specifies -ffoorrmmaatt ggiiff, then a handler named GIF87 or GIF89 may

be invoked, but a handler named JPEG may not (assuming that such han-

dlers had been registered).

When writing image data to a file, the processing of the -ffoorrmmaatt option

is slightly different: the string value given for the -ffoorrmmaatt 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 sup-

ported by the handler. Note that not all image handlers may support | writing transparency data to a file, even where the target image format | does. CCOOLLOORR AALLLLOOCCAATTIIOONN

When a photo image is displayed in a window, the photo image code allo-

cates colors to use to display the image and dithers the image, if nec-

essary, 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 True-

Color 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 -ppaalleettttee configuration option. If this

option is used, it specifies the maximum number of shades of each pri-

mary 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. CCRREEDDIITTSS