ColorThink Pro - Grapher

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Contents

The Grapher

Color information can be complicated - and 2D and 3D graphs aid visualization and help in evaluating profiles, devices and printing processes. The Grapher will plot the gamut volume (or outline) of ICC device and Space profiles - and the color list from Named Color Profiles (NCP) in (Y)xy, (L)uv, or (L)ab coordinates. It will also plot color lists resulting from measurement data, synthetic test data and image file colors. Device profiles include Scanner/Camera (“scan”), Monitor (“mntr”), and Printer (“pntr”) types. Device Link (“link”) and abstract (“abst”) profiles have no discernable gamut and therefore cannot be plotted as volumes. Their effects, however, can be graphed. For instance, an abstract profile can be applied to image / color data to create a vector graph.


Creating Graphs

Icon 2D.jpg Icon 3D2.jpg Click the 2D or 3D Grapher button on the Menu Bar to open an empty graph.

Controlling the Grapher

Zoom

The ColorThink Grapher was designed so manipulation of the plot item display was intuitive and powerful. The mouse plays an important role in this ability. A summary of its functions is:

Window size

The graph window and the Plot Items window can be re-sized to be larger or smaller as you wish. On Windows operating systems, click and drag any corner to change the size and shape of the window. On Mac systems, click and drag the lower right-hand corner.

Graph Elements

Graph Control Window

Example of the Graph Control window.
The graph control panel appears as a floating window in Windows and as a sheet attached to the Grapher window in Mac OS X. To show the graph control panel as a sheet, move the mouse pointer until it is just below the title bar of the Grapher window, centered near the “Grapher” window name. The sheet will slide out for you to make changes and then slide away when you move the point away from the control panel.

Dimensions

To select 2D or 3D: Click on the 2D or 3D radio button and ColorThink will change to that graphing mode.

example of a 2D graph
In each coordinate system, graphing in 2D removes the lightness component and the chromatic component is the only information plotted. As a result, the graphs show the outer edges of the gamut regardless of the lightness level of this information. For lightness information in addition to the chromatic information, use the Grapher in 3D mode.
3D graphs have the ability to display much more information than 2D graphs. Subtle gamut differences and color shifts are represented in 3D that are not possible in 2D. For example, in evaluating an inkjet printer which may be used for proofing purposes, it is important to determine that the inkjet can reach the same black point that the press or analog proof to be simulated is able to produce. In 3D it is immediately apparent when a proofer will not get dark enough whereas a 2D-gamut overlay would not reveal this information and the proofing printer might have mistakenly been deemed appropriate for the task.

Coordinates

To select the graphing dimension

Click on the Lab, Yxy, or Luv to change the graphing dimension:

The Yxy Chromaticy diagram is a popular 2D method for illustrating the gamut differences between different devices or printing methods. Yxy, however, is not perceptually uniform and so does not give an accurate illustration of gamut shape and size. For example, the greens in the Yxy diagram are exaggerated and plot covering a larger area than greens actually represent in our perception. For this reason Luv is included as a graphing coordinate system. Luv is designed to be more perceptually uniform than Yxy and the area devoted to each color more in line with our perception. The Lab coordinate system is also offered as a graphing option. Lab also offers a reasonable gamut shape and size representation but many claim also suffers from areas of perceptual non-uniformity.

In general we recommend the Yxy or Luv coordinates for 2D graphing only. Lab has been found to be easier to visualize, understand, and compare when creating 3D graphs.

Axes & Labels

Check the “Plot [vertical] axis” or “Plot [cross] axes options to plot lines for the axes. This can help with the visualization of color spaces

Spectrum Locus

Spectrum Locus
The Spectrum Locus is the curve defined by “pure” wavelengths of light plotted from 380nm to 730nm. The spectrum locus demarks the outer range of human perception – effectively the gamut of the human eye. The spectrum locus option is only available in the Luv and Yxy color spaces. Lab, by definition, is bounded by the human eye gamut. While Lab contains numbers that do not correspond to human-perceptible colors, the shape of the visible color gamut is difficult to determine and plot.

Background

Changing the Background slider will vary the brightness of the background.

Grid/Spin Tab

Example of the Grid/Spin tab

At the Grid/Spin tab, the grid lines can be turned on or off, including the foreground grid if desired. Turning off the grid can make it easier to see details in a profile, for example, without the grid obscuring the field of view. Capturing and compressing pictures and videos can often be done with a smaller file size when the grid is turned off.

ColorThink Pro Grapher
Spin Control

The spinning of the plot items in the graph can be controlled several ways:

The Slicer

Example of the slicer controls tab
Graph window with slicer turned on.

With the slicer turned on, a luminosity slider opens up on the graphing window, and a horizontal plane is "sliced" through the plot area. This allows the viewing of a profile, color list or image pixels at various sections of the color gamut. For example, individual pixels in an image can be compared to the gamut of the printer to be used.

Fine control of the slice

Besides using the Slicer L* drawbar, the slicer can be moved up and down using the arrow keys on the keyboard.


Also see Animating the Slicer.


Plot Item Control

Example of Plot Items window

To Add plot Items

° Drag the icon representing the item (color, color list, image, or profile) onto the Grapher window either from within ColorThink or directly from the Finder.
° Choose an item from the “Add” popup menu located immediately below the “Plot Items” listbox.
° Click the 2D or 3D Grapher button on the menu bar of the Profile Inspector, Image Inspector, or Color List windows.

Note: The Add menu contains a list of "Favorites" to make it easy to access many popular industry profiles. To add files to this Favorites area, place them in the following folder:
° C:\Program Files > CHROMiX > ColorThinkPro > Profiles (Windows)
° Applications > ColorThink Pro > Profiles

Images, color lists and shortcuts to other folders can also be placed within this Favorites area to customize it to your special needs.

To Remove plot Items

To Show or Hide Plot Item

Check or uncheck the box to the left of the plot item in the Plot Item Listbox.

Checking the box will also select the plot item. Unchecking a box will not select the plot item.

To Highlight a profile (2D only)


Setting Plot Item Colors

  1. Select an item in the plot list,
  2. Select:
  • True Colors All color points and vertices are colored using the actual Lab color values processed through the current monitor profile. Colors outside the gamut of the monitor will be plotted as the closest possible color (using the relative colorimetric rendering intent and the current CMM)
  • Single Colors All colors in the plot item will be colored using a single color. The next available single color will be selected for the plot item. To change the plot color, select a different color from the adjacent popup menu.
These delta E formulas are available when plotting as vectors
  • Delta-E Coloring (available in Vector mode only). Delta-E coloring will color the vectors (color shifts) in a plot item using green/yellow/orange/red depending on the amount of color shift depicted by the vector. To change the criteria for the error levels at which the color changes occur, select the “Delta-E Colors” tab and move the sliders in the color bar. In this manner you can select your shop-standard error levels and evaluate color shifts according to your own standards. In general, delta E 2000 is a more accurate choice for small differences. CMC 1:1 and CMC 2:1 are generally intended for use in the garment industry.

Note that while the Delta E coloring will change, the apparent length of the vectors in the Grapher will not change. The Lab space presented in the Grapher is by definition "delta-E 76" space, and the actual visual space within the Grapher cannot change. ColorThink provides the Delta-E coloring option so that users can have a quick visual display of color errors.

Tone using L*

Tone using L* - For true-color accuracy ColorThink darkens the colors plotted according to the Lightness (L* component of Lab) value of the color. This can cause dark colors to become invisible against dark backgrounds. Uncheck this box to remove the darkening effect and lighten the dark portion of the plot item. The colors are less accurate but details in shadow colors are much more visible.

Opacity

To vary the Opacity (transparency) of a plot item:

  1. Select the plot item in the list.
  2. Drag the Opacity slider left or right to decrease or increase the opacity of the plot item.

This is especially helpful for turning a profile gamut volume transparent so color data or other profile gamuts located inside or behind the current profile are visible. Please refer to the Tutorials section for an example of this technique.

Working with Color Lists

A color list can be a file that contains color information such as measurement data files, synthetic test data, a list from the Colors tab of the Color Worksheet, or even image files. A color list can be displayed on the grapher as points or as vectors.

The Grapher will only graph color lists that contain Lab values or spectral values. It will not graph color lists containing only RGB values or only CMYK values. The reason for this is that RGB or CMYK numbers represent device values which do not by themselves define a specific color (they only define how a color is produced on a certain machine.)

If you wish to graph a color list made up of device values, you can:

The software will automatically apply sRGB to your device values (unless you specify a different profile), and graph the color list accordingly.
Many programs, such as ColorPicker or ColorPort, offer several different choices for saving or exporting color lists. Choose one which includes Lab or spectral measurements.

An example of a Color List

ColorThink recognizes color lists that correspond to the CGATS format as well as several other common industry formats.

A simple color list can be easily created with a worksheet program (such as Excel) or using an ordinary text editor. This is essentially a text document with a few code words at the beginning and end, with your list of Lab values in-between.


Below is an example using Lab values. Note that:


BEGIN_DATA_FORMAT
Lab_L Lab_a Lab_b
END_DATA_FORMAT
BEGIN_DATA
91 -2 96
44 -29 2
END_DATA


Don't forget to include "END_DATA" on the last line. Feel free to copy and paste the code above and use it as a template for your data.

As Points

Example of the "Plot as Points" option


Join with lines make it easier to follow related colors.

Join With Lines

The primary intent of Join with Lines is to help those analyzing their primary and secondary colors by making it easier to see which colors belong in which group, especially when looking at very irregular profiles. The Evaluate Device Linearity procedure in the ColorSmarts Guide ColorSmarts Guide is an example of how this is used to great effect.

ColorThink makes this feature available to all points in case the user finds it useful.

What determines how lines are drawn

The software code looks at the first three characters in the name of each color in the colorlist. If the first three characters are the same, ColorThink will draw a line between them.

The first 3 characters of the color names are the same

example of join with lines


Example of what vectors look like. (Click to enlarge.)

As Vectors

Plotting colors as vectors allows a graphical view of color shifts in 2 or 3 dimensions. This is a powerful technique to quickly get a feeling for how color shifts are occurring in different colors (different areas of the 3D color space) and what types of shifts (lightening/darkening, hue shifts, saturation changes) are occurring.

Vectors can be used to:

The vectors will look like little tadpoles. The dot will appear at the end of the vector and represent the color that is second in the list of plot items. Think of it as the first list is the "before" and the second list the "after".

This feature can be very useful for viewing device drifts, how different printer/ink/media settings affect color, or how different filters on your reading device affect the color values.

Enabling Vectors

  1. Select an Image or Color List plot item and click the “Vectors” button.
  2. A “destination” box will appear.
  3. Drag your comparison data or a profile into the destination box.

Comparison data would consist of another color list. It is suggested the original color list and the “destination” color list have the same number of colors. If the number of colors in each list differs, ColorThink will plot all the vectors for which a color exists in each list. Additional colors in the longer list will be ignored.

If you drag a profile into the “destination” box, ColorThink will “round trip” the color list and show the color shift that occurs as a result of this conversion. This round trip consists of a conversion from Lab to the color space of the device profile and then a conversion back to Lab using the same profile. Assuming the “back” or “proofing” conversion of the profile is accurate, this round trip transform will show how much color shift occurs as a result of the profile application. You will see out-of-gamut colors shift in-gamut to as to become printable, in-gamut colors shift due to perceptual renderings or profile errors.

A method of using vectors to compare the colors of two different images is presented in the See differences between images in Grapher section on the Worksheet.

Rendering Intent (profiles only)

To change the rendering intent used for the conversion (the Lab->device part of the conversion):

Coloring by delta-E - see delta-E color in Plot Item Control above.

Working with Profiles

As Volumes

When plotting profiles, ColorThink shows the device gamut captured by the profile using a gamut volume shape (for 3D graphs) or a gamut outline (for 2D graphs). The appearance of that volume can be in three different styles:

  1. Wireframe is the simplest plot and joins the vertex points together using lines. Linearity/calibration of the profiled device shows as differing spaces between the lines.
  2. Flat Each 4-sided polygon on the gamut surface is rendered using a single, solid color. This effectively shows the gamut volume, the linearity/calibration of the device and the color representation of the locations in the Lab colorspace.
  3. Smooth Each polygon’s color is rendered smoothly, blending the different corner colors across the surface of the polygon. This is the most accurate color rendering of the surface of the device gamut but at the expense of gamut surface detail.

Resolution

A 2D gamut of GRACoL2006 using minimum resolution

Some profiles might have small fluctuations along the gamut boundary. In these cases a higher resolution can be selected to provide more precise gamut calculations. Be aware, however, that the choice of a more precise resolution (5% or 1%) will require more processing time, and it may take longer to create the gamut plot.

Minimum creates a gamut shape using only the 100% primary and secondary colors, plus a black point and a white point. The minimum resolution setting can be useful in comparing ColorThink 2D graphs with other elementary graphs which are limited to basic hexagonal shapes. Using minimum superimposed on the same profile displayed as points can aid in demonstrating hue "hooking".

To change profile volume resolution:
At the "Res" drop-down box...
Plotting points with primaries and secondaries, compared with the same profile using "minimal" resolution.

Device Gamut

By default, ColorThink Pro will graph the device gamut of an output profile. This will give the most accurate representation of what the particular device (ie: printer, press) is capable of. This graphs the color as it is delivered to the profile connection space (PCS). This is known as the A to B (or the RGB/CMYK to Lab) transform of the profile. Another way to put this is that you're looking at the proofing action of the profile rather than the printing action. By default, the Device Gamut radio button is selected.

Choosing any of the rendering intents with the other radio button will change the graph to display other rendering intents in the A to B transform. Please note that this is the A to B transform shown, the conversion to Lab. It is not the B to A transform. (This setting can be useful for some who are evaluating part of a profile's tables or in showing how data is handed off to the second profile in a transformation, but this is a very advanced, technical use - and of limited use in workflow analysis.) This graph does not show what effect different ink limiting or black generation will have on the printing. These are represented in the B to A side of a device profile.


In order to view an effect of the B to A transform, try the procedure shown in this YouTube video. This demonstrates a method for seeing the actions of the "printing" direction of the profile: Viewing a Rendered Gamut Video

Constrain Channels

Move the sliders to see the gamut change

The Constrain Channels feature plots a volume as if each ink channel had been limited according to the values of the slider.

Possible uses:

While this is primarily intended for CMYK profiles, the constrain channels feature is also available for RGB profiles, to help learn or demonstrate how red, green and blue make up the profile.

ColorSmarts Guide
Try out the "Evaluate Optimal Device Ink Limits" procedure in the ColorSmarts Guide to see this function in practice.


Seeing the difference

Making use of different colors and varying gamut opacities can aide in easily seeing the difference between two device gamuts.

As Points

Plotting a profile volumes as points
Primary and secondary colors.
Neutral gray plot
  • - The points on the surface of the gamut,
  • - Only the primary colors (Red, Green and Blue) within the profile
  • - Only the primary and secondary colors (Red, Green, Blue, Cyan, Magenta & Yellow) within the profile
  • - The RGB Device Neutral colors (grays).

Plotting a profile as points and using a narrow point set allows you to identify the action of the individual inks in an inkjet printer. Used in conconction with "connect with lines" this can allow you to visually see problems such as hooks in ink saturation, linearization problems, black and white printing color casts and more.

ColorSmarts Guide
Many of these functions are automated for you in the ColorSmarts Guide section of ColorThink Pro. Try "Evaluate Device Linearity", "Evaluate Device RGB Calibration", "Evaluate Device Tone Stability" and others.



Working with Images and Lists

an image graphed in ColorThink is shown superimposed on an sRGB gamut volume

ColorThink will graph .tif images and .jpg images. For best results, we recommending using uncompressed, 8-bit, .tif images which are relatively small in size (scaled down if necessary) so that pixel calculations will not take too long.

When an image is brought into the Grapher with an embedded profile attached to it, ColorThink Pro will use the embedded profile to determine the graph points. When there is no profile attached to an image, it will plot the image in a default color space, such as sRGB (for RGB files,) and U.S. Web Coated (SWOP) v2 (for CMYK profiles).

Keep in mind that ColorThink Pro attempts to map every pixel in your image to its respective point on the 3D graph space.

This is a powerful tool, but one that can require a lot of computation time. It is recommended that the user downsample images to less than 1 Megapixels in size before importing into the Grapher if speed and CPU capacity is limited.

Another means of dealing with large images is to:

This procedure creates a color list for each of the colors in the image (which are different enough to be humanly distinguishable). This list can be graphed without concern for the file size, and yet all the colors in the original image will be represented in the graph.

Due to the slight warping of Lab space, and the rounding of color numbers in the process of quantifying colors, the Grapher might not display every single pixel in an image.

Saving Graph images

Windows
Mac

ColorThink Pro can save the graph window as an image in either "BMP" format (Windows version) or "PICT" format (Mac version).

1] Go to File, Save as BMP image (Windows) or Save as PICT image (Mac)

2] Choose a file name for the image and the location at which you wish to store it.

Note: The size of the saved image file is dependent on the size of the grapher window. See Window size for instructions on how to change the size of the grapher window.


Note: Some Windows 7 users have reported that the "Save dialog" window shows up in the saved BMP image of the Grapher, despite several attempts to move it out of the way during the save process. If this occurs, try running the program as an administrator. (Start the program by right-clicking the "ColorThink Pro.exe" file, and choose "Run as administrator."


Quicktime Video

Saving Graph as QuickTime Video file

You can also save the action in the graph window in motion in a QuickTime video. This allows the sharing of 3D graphing with anyone who has a QuickTime viewer. With this feature, a movie is automatically made showing everything in the grapher window revolving a complete 360o turn. This can be done using profiles, images, color lists, and with or without the slicer. See Animating the Slicer.

Anyone can view your movie by downloading the free version of Quicktime player: http://www.apple.com/quicktime/download

At this time, Quicktime is limited in that movie files made on a Mac computer can only be viewed by Quicktime on another Mac computer. In the same way, movies to be viewed on a Windows computer need to be created on another Windows computer.

Update: In limited testing with Quicktime X, (a version of Quicktime that runs on the Mac operating system Snow Leopard {10.6}) we have found that when a ColorThink Pro movie is brought into Quicktime X, and saved out again - this file CAN be viewed on both Windows and Mac Quicktime installations.

CTP movie1.jpg
CTP movie2.jpg

Steps

1] Go to File, Save as Quicktime Video

2] Choose the frame rate.

3] If "Specify Quicktime Options" is checked, you will be given options for compression format and quality in the next step.

4] If the slicer has been turned on in the Grapher, the animate slicer option is activated when saving a QuickTime movie.

Compression options for Mac
Compression options for Windows

5] The Compression Settings dialog box comes up if Specify QuickTime Options has been checked in #3] above. This allows the user to specify how many frames per second are to be captured, which compression type is to be used, and the quality of the compression of the video. In general, when a large number of frames per second are chosen, the file size will be larger. Also, a high quality compression will increase the file size of the movie.

The size of the grapher window determines the size of the final movie, so size your grapher window accordingly. See Window size for more information.

File sizes can be reduced by making your movie window smaller or by using less complicated images. Most compression algorithms will be more efficient with simpler graphs, so turn off the grid and simplify the background to reduce the file size of the movie.

There is a very large selection of available compression types to choose from. These choices are part of the Quicktime program, and will change depending on which version of Quicktime you have on your system. We find that Photo - Jpeg works well and provides a good quality image.

Quicktime offers a "loop" feature that allows you to run your movie continuously. To have your movie of the grapher continuously revolve smoothly, be sure that your total number of frames in the movie are divisible by the frames-per-second number.

Animating the Slicer

A Quicktime video can be made with the Slicer turned on. This option will move the Slicer from the top of the gamut to the bottom and back up to the top again, as it proceeds through one full rotation (360o) of the 3D graphing window. To capture the full range of the Slicer movement you must choose to make a movie with 48 frames. (Less frames will result in the Slicer not going all the way down.)

Keyboard Shortcuts

While in the Grapher...

To Save a Graph

Press control/command-S to save an image file of the graph window.

To Save a QuickTime movie

Press shift-control/command-S to save a Quicktime movie of the graph window.

To Open a profile from the Plot list into the Profile Inspector

Double-click the profile in the Plot list.

To open a gamut of points into the worksheet as a colorlist

Hold down the option key and double-click the profile in the plot list.
Click the question mark (?) to bring up the Grapher Help page

Grapher Help

There is also a Grapher Help page which lists many of these shortcuts. Click the blue ? in the top right corner of the Plot Items pane.

Keyboard Shortcuts:

delete - removes item from plot list
left/right arrows - rotate graph left / right, nudges rotation if using intertia (3D)
up/down arrows = rotate graph up/down (3D)
space - stop rotation if using inertia
g - gridlines on/off
s - slicer on/off
t - "Tone using L*" on/off
command/control - 2/3 - toggle between 2D and 3D mode

Mousing:

shift-drag - move graph around left/right(3D) and up/down
option/alt-drag - zoom in/out using mouse up/down movement
command/control-drag - move slicer up/down

Numeric Keypad:

2, 8 - rotate graph up/down (3D)
4, 6 - rotate graph left/right (3D)
5 - stop rotation if using inertia (3D)
'-' - slicer on/off

Go on to Part 1 of the Color Worksheet

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