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A bitmap is an image whose pixels can display either of two colors or be transparent. A bitmap image is defined by four things: a background color, a foreground color, and two bitmaps, called the source and the mask. Each of the bitmaps specifies 0/1 values for a rectangular array of pixels, and the two bitmaps must have the same dimensions. For pixels where the mask is zero, the image displays nothing, producing a transparent effect. For other pixels, the image displays the foreground color if the source data is one and the background color if the source data is zero.

Creating bitmaps

Like all images, bitmaps are created using the image create command. Bitmaps support the following options:

-background color: Specifies a background color for the image in any of the standard ways accepted by Tk. If this option is set to an empty string then the background pixels will be transparent. This effect is achieved by using the source bitmap as the mask bitmap, ignoring any -maskdata or -maskfile options.
-data string: Specifies the contents of the source bitmap as a string. The string must adhere to X11 bitmap format (e.g., as generated by the bitmap program). If both the -data and -file options are specified, the -data option takes precedence.
-file name: name gives the name of a file whose contents define the source bitmap. The file must adhere to X11 bitmap format (e.g., as generated by the bitmap program).
-foreground color: Specifies a foreground color for the image in any of the standard ways accepted by Tk.
-maskdata string: Specifies the contents of the mask as a string. The string must adhere to X11 bitmap format (e.g., as generated by the bitmap program). If both the -maskdata and -maskfile options are specified, the -maskdata option takes precedence.
-maskfile name: name gives the name of a file whose contents define the mask. The file must adhere to X11 bitmap format (e.g., as generated by the bitmap program).

Image command

When a bitmap 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. The following commands are possible for bitmap images:

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 bitmap 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 Tk_ConfigureInfo 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 image create bitmap command.

Licensed under Tcl/Tk terms
https://www.tcl.tk/man/tcl/TkCmd/bitmap.htm