img - Introduction to Img
Img is a Tk extension, adding support for many image formats.
Sources and binaries of Img are available at SourceForge.
The individual formats are described in more detail on their own pages.
Windows bitmap format. See img-bmp.
Digital Terrain Elevation Data format. See img-dted.
FLIR FPF Public Image format. See img-flir.
Graphics Interchange Format. See img-gif.
Windows icon format. See img-ico.
Joint Picture Experts Group format. See img-jpeg.
Paintbrush format. See img-pcx.
Pixmap image type. While the other formats are handlers for the Tk photo image type, this is a new image type for Tk. See img-pixmap.
Portable Network Graphics format. See img-png.
Portable pixmap format. See img-ppm.
Postscript and PDF format. Requires an external application, ghostview for its operation. See img-ps.
Raw data format. See img-raw.
Silicon Graphics format. See img-sgi.
Sun raster format. See img-sun.
Truevision Targa format. See img-tga.
Tagged Image File Format. See img-tiff.
Tk window as photo image. See img-window.
X Windows Bitmap format. See img-xbm.
X Windows Pixmap format. See img-xpm.
Img version 2 only works with Tcl/Tk 8.6 or newer. If using an older Tcl/Tk version, use the lastest Img 1.4 version.
Formats marked with * are not loaded when doing a package require Img, but must be loaded explicitly via package require img::FORMAT.
Some image formats support storage of multiple pages in a file.
Supported by formats img-gif, img-ico, img-ps, img-tiff.
A specific page can be extracted using the -index option. Index 0 specifies the first page.
There is currently no support for writing multi-page images.
The number of pages of an image file can either be retrieved using metadata key numpages (see chapter Image Metadata) or by checking different -index values.
For example, GIF images can have multiple pages in one file. The metadata dictionary key numpages is not supported for GIF images, as this property cannot be extracted fast.
If you need to know the number of pages, use code like in the following example:
proc CheckIndex { fileName fmt ind } { set retVal [catch {image create photo -file $fileName -format "$fmt -index $ind"} phImg] if { $retVal == 0 } { image delete $phImg return true } return false } proc GetNumPages { fileName fmt } { if { [CheckIndex $fileName $fmt 1] } { set ind 5 while { [CheckIndex $fileName $fmt $ind] } { incr ind 5 } incr ind -1 while { ! [CheckIndex $fileName $fmt $ind] } { incr ind -1 } return [expr { $ind + 1 }] } return 1 } # Determine the number of pages of an animated GIF. set numPages [GetNumPages $imgFile "gif"]
Some image formats support an individual set of metadata dictionary keys. See the Tk photo command for more information regarding image metadata.
This support is enabled, if Img is linked against Tk 8.7 or newer.
The following keys are supported:
Horizontal image resolution in dots per inch as double value.
Supported by formats img-bmp, img-jpeg, img-pcx, img-png, img-tiff.
Aspect ratio defined as horizontal size divided by vertical size as double value.
Supported by formats img-bmp, img-jpeg, img-pcx, img-png, img-tiff.
The number of pages in an image file.
All formats supporting image resolution (DPI and aspect) have the following format options for writing these values without explicitly setting the metadata dictionary:
-resolution -xresolution -yresolution.
Options -xresolution and -yresolution must both be specified. Otherwise no resolution information is written.
Resolution values specified with any of the above options overwrite the corresponding dictionary values.
The resolution values can be specified as double values as documented with function Tk_GetPixels.
Example resolution specifications:
1.0: 1 inch 1i : 1 inch 1c : 1 centimeter 1m : 1 millimeter 1p : 1 point
Example writing PNG image with horizontal resolution of 300 inches and vertical resolution of 200 centimeters:
img write out.png -format {png -resolution 300i 200c}
Some image formats support pixel values greater than storable in 8-bit integers.
The following formats support 16-bit integer pixel values: img-dted, img-ppm.
The following formats support floating point pixel values: img-flir, img-raw.
To map these values to 8-bit integer values as needed for a Tk photo, two different algorithms are implemented in Img:
A simple MinMax algorithmn and an advanced Automatic Gain Control (AGC) algorithmn using histogram equalization.
The default for all supported formats is to use the MinMax algorithm, which determines the minimum and maximum values of the image automatically.
img, img-bmp, img-dted, img-flir, img-gif, img-ico, img-jpeg, img-pcx, img-pixmap, img-png, img-ppm, img-ps, img-raw, img-sgi, img-sun, img-tga, img-tiff, img-window, img-xbm, img-xpm
Copyright © 1995-2024 Jan Nijtmans <nijtmans@users.sourceforge.net>
Copyright © 2002-2024 Andreas Kupries <andreas_kupries@users.sourceforge.net>
Copyright © 2003-2024 Paul Obermeier <obermeier@users.sourceforge.net>