TWEAK(1)						      General Commands Manual							  TWEAK(1)

NAME

       tweak - edit bitmap files, subfont files, face files, etc.

SYNOPSIS

       tweak [ file ...  ]

DESCRIPTION

       Tweak edits existing files holding various forms of bitmap images.  To create original images, use art(1) or start from an existing bitmap,
       subfont, etc.

       Tweak reads its argument files and displays the resulting bitmaps in a vertical column.	If the bitmap is too wide to fit across  the  dis-
       play,  it  is  folded  much like a long line of text in an 81/2 window.	Under each bitmap is displayed one or two lines of text presenting
       parameters of the image.  The first line shows the bitmap's ldepth, the log base 2 of the number of bits per pixel; r, the  rectangle  cov-
       ered  by the image; and the name of the file from which it was read.  If the file is a subfont, a second line presents a hexadecimal 16-bit
       offset to be applied to character values from the subfont (typically as stored in a font file; see font(6)); and the subfont's  n,  height,
       and ascent as defined in cachechars(2).

       By  means described below, magnified views of portions of the bitmaps may be displayed.	The text associated with such a view includes mag,
       the magnification.  If the view is of a single character from a subfont, the second line of text shows the character's value (including the
       subfont's  offset) in hexadecimal and as a character in tweak's default font; the character's x, top, bottom, left, and width as defined in
       cachechars(2); and iwidth, the physical width of the image in the subfont's bitmap.

       There are two methods to obtain a magnified view of a character from a subfont.	The first is to click mouse button 1 over the image of the
       character  in the subfont.  The second is to select the char entry on the button 3 menu, point the resulting gunsight cursor at the desired
       subfont and click button 3, and then type at the text prompt at the bottom of the screen the character value, either as a multi-digit hexa-
       decimal number or as a single rune representing the character.

       To  magnify  a portion of other types of bitmap files, click button 1 over the unmagnified file.  The cursor will switch to a cross.  Still
       with button 1, sweep a rectangle, as in 81/2, that encloses the portion of the image to be magnified.  (If the file is  16x16  or  smaller,
       tweak will just magnify the entire file; no sweeping is necessary.)

       Depressing buttons 1 and 2 within magnified images changes pixel values.  By default, button 1 sets the pixel to all ones and button 2 sets
       the pixel to all zeros.

       Across the top of the screen is a textual display of global parameters.	These values, as well as many of  the  textual	values	associated
       with  the images, may be edited by clicking button 1 on the displayed value and typing a new value.  The values along the top of the screen
       are:

       mag    Default magnification.

       val(hex)
	      The value used to modify pixels within magnified images.	The value must be in hexadecimal, optionally preceded by a tilde for  bit-
	      wise negation.

       but1

       but2   The  boolean  function  used  by	the  named button to set pixel values.	The function may be specified either by name as defined in
	      <libg.h>, e.g.  DorS, or by simple boolean expression, e.g.  S|D.  In these expressions, S is the pixel value defined above and D is
	      the pixel being modified.

       copy   The boolean function used in the copy menu item.

       Under  button 3 is a menu holding a variety of functions.  Many of these functions prompt for the image upon which to act by switching to a
       gunsight cursor; click button 3 over the selection, or click a different button to cancel the action.

       open   Read and display a file.	The name of the file is typed to the prompt on the bottom line.

       read   Reread a file.

       write  Write a file.

       copy   Use the copy function, default S, to transfer a rectangle of pixels from one image to another.  The program  prompts  with  a  cross
	      cursor;  sweep out a rectangle in one image or just click button 3 to select the whole image.  The program will leave that rectangle
	      in place and attach another one to the cursor.  Move that rectangle to the desired place in any image and click button 3, or another
	      button to cancel the action.

       char   As described above, open a magnified view of a character image in a subfont.

       close  Close the specified image.  If the image is the unmagnified file, also close any magnified views of that file.

       exit   Quit tweak.  The program will complain once about modified but unwritten files.

       To clear blocks of pixels, use copy with function 0.

SOURCE

       /sys/src/cmd/tweak.c

SEE ALSO

       art(1), cachechars(2), bitmap(6), font(6)

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