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
Under each image is displayed one or two lines of text
presenting its parameters.
The first line shows the images
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
and the subfonts
ascent as defined in
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 characters value (including the subfonts offset)
in hexadecimal and as a character in
tweaks default font; the characters
width as defined in
iwidth, the physical width of the image in the subfonts image.
There are two methods to obtain a magnified view of a character from a
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 16×16 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:
The value used to modify pixels within magnified images.
The value must be in hexadecimal, optionally preceded by a
tilde for bitwise negation.
The pixel value written when the corresponding button is pressed over a pixel.
Whether the pixel values are inverted when a
copy operation is performed.
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.
Read and display a file. The name of the file is typed to the prompt
on the bottom line.
Reread a file.
Write a file.
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.
As described above, open a magnified view of a character image in a subfont.
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.
Close the specified image.
If the image is the unmagnified file, also close any magnified views of that file.
tweak. The program will complain once about modified but unwritten files.