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 NAME     
 |  |  |  | tweak – edit image files, subfont files, face files, etc. 
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 SYNOPSIS     
 DESCRIPTION     
 |  |  |  | Tweak edits existing files holding various forms of images. To
    create original images, start from an existing image, subfont,
    etc. 
    
    
    Tweak reads its argument files and displays the resulting images
    in a vertical column. If the image is too wide to fit across the
    display, it is folded much like a long line of text in an rio
    window. Under each image is displayed one or two lines of text
    presenting its parameters. The first line shows the image’s depth,
    the number of bits per pixel; r, the
    rectangle covered 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(7));
    and the subfont’s n, height, and ascent as defined in cachechars(3).
    
    
    
    By means described below, magnified views of portions of the images
    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(3);
    and iwidth, the physical width of the image in the subfont’s image.
    
    
    
    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 hexadecimal
    number or as a single rune representing the character. 
    
    
    To magnify a portion of other types of image files, click button
    1 over the unmagnified file. The cursor will switch to a cross.
    Still with button 1, sweep a rectangle, as in rio, 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.) 
    
    
    Pressing buttons 1 and 2 within magnified images changes pixel
    values. By default, button 1 sets the pixel to all zeros and button
    2 sets the pixel to all ones. 
    
    
    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)
 
 but1|  |  |  | The value used to modify pixels within magnified images. The value
        must be in hexadecimal, optionally preceded by a tilde for bitwise
        negation. 
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 but2   The pixel value written when the corresponding button is pressed
    over a pixel.
 invert−on−copy
 
 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.|  |  |  | Whether the pixel values are inverted when a copy operation is
        performed. | 
 open   Read and display a file. The name of the file is typed to
    the prompt on the bottom line.
 read   Reread a file.
 writeWrite 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
 char   As described above, open a magnified view of a character image
    in a subfont.|  |  |  | in any image and click button 3, or another button to cancel the
        action. 
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 pixels
 
 closeClose the specified image. If the image is the unmagnified
    file, also close any magnified views of that file.|  |  |  | Report the coordinate and value of individual pixels indicated
        by pressing button 3. This is a mode of operation canceled by
        pressing button 1 or 2. 
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 exit   Quit tweak. The program will complain once about modified
    but unwritten files.
 
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 SOURCE     
 SEE ALSO     
 BUGS     
 |  |  |  | For a program written to adjust width tables in fonts, tweak has
    been pushed unreasonably far. 
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