Graphical user interface for digital image editing

Chromatic adjustments to the overall color balance of the image are presented on one screen and tonal adjustments (such as brightness or contrast) that do not affect the overall color balance are presented on another screen. The chromatic adjustments include at least three independent variables each of which can be separately increased or decreased, while the tonal adjustments include brightness and contrast that can be separately increased or decreased. Such a grouping concentrates the user's attention on only two or three adjustments related to a single readily identifiable deficiency in the original image, and thus not only facilitates image improvement but also makes it easier to selectively undo the effects of some adjustments but not others. Each adjustment is displayed as a pair of preview images which respectively show the effect of a one step increment or decrement of the associated variable. Each pair of preview images are clearly separated from all other images on the same screen and are displayed as two adjacent "buttons" either of which can be actuated by the user to effect the displayed result. The step size is adjustable by means of a single slider control that is effective for all the adjustments on that screen Each image adjustment screen includes thumbnail images corresponding to the original image and to the revised image. The thumbnail revised image is the largest image on the screen and is the focal point of attention for the user.

FIELD OF THE INVENTION 
The present invention relates generally to computerized manipulation of 
digitized images, and more particularly to a graphical user interface for 
assisting a user to make desired adjustments in a displayed continuous 
tone image. 
BACKGROUND OF THE INVENTION 
PC (personal computer) based graphics software systems are commercially 
available for professional photographers and other experts in digital 
imaging. They typically permit the user to increment (or decrement) 
individual variables such as brightness, contrast, or hue, and to see 
previews (thumbnails) of a single increment of change in two or more 
related variables before the selected change is applied to the underlying 
data. However, many variables can be manipulated on the same screen, the 
interrelationships between the various variables are not readily apparent, 
and many combinations of interrelated variables are not previewed. As a 
result, the novice user is overwhelmed with information and choices that 
have no apparent relationship to a desired change to the displayed image, 
Particularly when attempting to edit a color image, a novice user without a 
basic understanding of color science does not know how to translate a 
desired improvement in an image into the specific values for the Red, Blue 
and Green (RBG), or Cyan, Magenta, Yellow and Black (CMYK) parameters 
corresponding to the input and output signal channels associated with 
color scanners, color monitors, color printers and other color-oriented 
electronic devices. Indeed, many users do not realize that Magenta is the 
opposite of Green, that Cyan is the opposite of Red, and that Yellow is 
the opposite of Blue. 
A general purpose graphical user interface such as Microsoft Windows.TM. 
permits the programmer to designate certain portions of the screen as 
"buttons" which may be selected and operated by positioning and actuating 
a pointer device such as a "mouse". When the button is so actuated, the 
user receives an acknowledgment in the form of a visible change to the 
button's appearance, and the user interface invokes a software process 
designated by an "icon", text, or other graphics on or adjacent to the 
button. 
However, the known user interface designs for graphics software 
applications do not provide an intuitive and unambiguous way for the 
novice user to make a reversible sequence of simple image adjustments such 
as more blue followed by less blue. As a result, many users of graphics 
software do not even try to change the color or other tonal characteristic 
of an image because they fear that they will make the image look worse 
instead of better. 
SUMMARY OF THE INVENTION 
In accordance with one aspect of the invention, chromatic adjustments to 
the overall color balance of the image are presented on one screen and 
tonal adjustments (such as brightness or contrast) that do not affect the 
overall color balance are presented on another screen. Preferably, the 
chromatic adjustments include at least three independent variables each of 
which can be separately increased or decreased, while the tonal 
adjustments include at least two independent variables that can be 
separately increased or decreased. Such a grouping concentrates the user's 
attention on only two or three adjustments related to a single readily 
identifiable deficiency in the original image, and thus not only 
facilitates image improvement but also makes it easier to selectively undo 
the effects of some adjustments but not others. 
In accordance with another aspect of the invention, each adjustment is 
displayed as a pair of preview images which respectively show the effect 
of a one step increment or decrement of the associated variable. 
Preferably, each pair of preview images are clearly separated from all 
other images on the same screen and are displayed as two adjacent 
"buttons" either of which can be actuated by the user to effect the 
displayed result. The step size is preferably adjustable by the user by 
means of a single control that is effective for all the adjustments on 
that screen This results in an adjustment mechanism that is reversible and 
readily understandable, even to the novice user. 
In accordance with yet another aspect of the invention, each image 
adjustment screen includes thumbnail image corresponding to the original 
image and to the revised image. Preferably, the various thumbnail and 
preview images correspond to a selected portion of the original image, and 
Zoom and Pan controls are provided to enable the user to select which 
portion is to be displayed. Size and position may be used to distinguish 
between the various preview and thumbnail images displayed on the same 
screen, with the thumbnail view of the revised image being more prominent 
than the thumbnail view of the original image, and with the thumbnail view 
of the original image being more prominent than any of the preview views. 
This makes the picture the focal point of attention for the user, and 
gives the user a higher fidelity representation of the final result of the 
adjustments made in the screen. In contrast, the preview images are merely 
presented as a mechanism to achieve that result, for example as animated 
buttons.

DETAILED DESCRIPTION 
Referring to FIG. 1, it will be seen that a typical PC-based image 
processing system 10 incorporates a flat bed scanner 12 (or other digital 
image source), a personal computer 14 (or other digital image processor) 
with a monitor 16 and mouse 18, and a color ink jet printer 20 (or other 
output device). Except for certain aspects of the software, to be 
discussed in more detail hereinafter with respect to FIGS. 2-4, the image 
processing system may comprise commercially available hardware and 
software components, assembled in a manner that will be readily apparent 
to one skilled in the art. 
In an exemplary embodiment as shown in simplified block diagram form in 
FIG. 2, the software 22 that controls PC 14 includes an operating system 
24 (such as Microsoft Windows 95) having a generic graphical interface 26 
whereby the user may use the pointer 18 via a pointer driver 28 to select 
and operate various controls (such as buttons and sliders) appearing on 
the screen of the monitor 16 under the control of a display driver 30 
thereby generating control signal inputs 32 to an application program such 
as image processor program 34. The control signals 32 include a first set 
associated with a chromatic adjustment routine 36: IN, OUT, LARGE, SMALL, 
BLUE, YELLOW, GREEN, MAGENTA, RED, CYAN, REVERT, and a second set 
associated with a tonal adjustment routine 38: IN, OUT, LARGE, SMALL, 
LIGHT, DARK, HIGH LOW and REVERT. Image processor 34 also includes memory 
40 for storing in known fashion a thumbnail of the original image (i.e., 
before the current set of adjustments were applied, but including any 
previously saved adjustments, as well other corresponding images that 
incorporate various selected combinations of adjustment steps. Image 
processor 34 receives image data from scanner 12 via a scanner driver 42 
and outputs image data not only to the monitor 16 via the graphics 
interface 26, but also via printer driver 44 to printer 20. 
Reference should now be made to FIG. 3, which shows a presently preferred 
embodiment of the control screen 46 associated with color adjustment 
routine 36. The depicted image is a simple geometric array of colored 
stripes, with the green stripes 48 extending upwardly from left to right, 
the blue stripes 50 extending horizontally, and the red strips 52 
extending downwardly from left to right, with the intensity of each color 
being represented schematically by the width of each stripe. However, it 
will be appreciated that the principles of the invention are applicable to 
more complex images formed from many individual pixels, with each pixel 
including having components selected from three primary colors, with each 
component capable of assuming many different intensity levels. 
At the center of screen 46 is a thumbnail 54 of a selected portion of the 
image as currently revised, including any prior adjustments. It is the 
center of the screen 46 and therefor the natural focus of the user's 
attention. Surrounding the revised thumbnail 54 are six smaller preview 
images 56Grn 58Grn 58Blu 56Blu 58Red 56Red which display the same image, 
to which has been tentatively applied a predetermined number (n) of color 
adjustment steps as follows (counterclockwise starting at the upper left): 
+n green, -n green, -n blue, +n blue, -n red, +n red. 
Note that in color space, Green is the opposite of Magenta and that adding 
one unit of Green is the same as subtracting one unit of Magenta and vice 
versa. Similarly, Blue is the opposite of Yellow, and Red is the opposite 
of Cyan. 
To further emphasize and identify the function of each preview image, the 
preview image 56 associated with a positive increment is provided with a 
corresponding plus icon 60 on an appropriately colored background and the 
preview image 58 associated with a negative increment is provided with a 
corresponding minus icon 62. Both the pair of preview images 56, 58 and 
the associated plus and minus icons 60, 62 are displayed in the form of 
button graphics, either of which when selected and operated by the user, 
causes the revised thumbnail image 54 to incorporate the selected 
adjustment, whereupon all previews 56, 58 are updated accordingly. 
Conventionally, color correction requires manipulation of three independent 
variables. In accordance with the present invention, the adjustment of 
each variable is displayed as two side-by-side preview images 56, 58 which 
respectively show the effect of a one step increment or decrement of that 
variable. Moreover, each pair of preview images 56, 58 are clearly 
separated from all other images on the same screen. 
Intermediate in size between the Revised thumbnail and the six previews is 
an Original view 64 of the image as last saved by means of "OK" button 66. 
The user may exit from screen by means of Cancel button 68. Alternatively, 
the use may revert to the last saved image as displayed on Original button 
64 by either selecting and operating the button on which that image is 
displayed, or by operating the "Revert to Original" button 70. A slider 
control 72 is also provided to simultaneously set the current step size 
from one unit (extreme left) to five units (extreme right), and which is 
effective for all the adjustments on that screen. Counters 74 are provided 
to indicate the number of units of each adjustment that have been applied 
to the original image 64 since it was last saved by means of OK button 66. 
A pair of conventional zoom controls 76, 78 can be used to select how much 
of the image is displayed in each of the windows 64, 54, 56, 58. A 
conventional pan control (not shown) may also be provided to select a 
portion of the displayed image other than its center. 
Reference should now be made to FIG. 4, which depicts a Tonal Control 
screen 80 implementing similar concepts as used in the design of Color 
Control screen 46, but applied to only two variable variables, namely 
Brightness and Contrast. Accordingly, corresponding elements have been 
identified with the same reference numeral as was used previous, but with 
the suffix "a", "Br" or "Co". The schematic images are a series of 
vertical stripes representing an image gradient that is dark on the left 
and bright on the right, with the width of each stripe representing the 
tonality of that part of the image, ranging from very dark (left) to very 
light (right). 
Note that the Tonal screen 80 is very similar in arrangement and appearance 
to Color screen 46, except for the number of paired preview images 56, 58 
and associated plus and minus icons 60, 62 (two instead of three). 
However, the background of the plus and minus icons 60Br, 62Br for the 
brightness adjustment is solid black, while for contrast icons 60Co, 62Co 
it is black and white (more contrast 60Co), or dark gray/light gray (less 
contrast icon 62Co). 
Other modifications will be apparent to those skilled in the art. For 
example, some of the previews 56, 58 could depict only a selected portion 
of the original image, while the windows 64, 54 could depict the entire 
image. As another example, the revert button 70 could be programmed to 
provide more than one undo level.