mardtb 248x110
Edited on 11-Jul-2017


3. Image


3.1 Introduction

Image

The "Image"-page can be accessed by selecting the corresponding tab in the main window or by pressing the "Ctrl+1"-key while the pointer is in the main window. This window is the area where to visually inspect images. The data display functions are very similar to those used by program marView with a couple of restrictions. You can:

The "Image"-page features several areas:


During data collection, incoming images are loaded and displayed automatically, but only if the "Image"-page is up or if the Image menu-choice "Display image after scan" is selected. One should keep in mind, that image display puts load on the computer. During a data collection, it may not really be necessary to keep looking at images if everything proceeds nicely.


3.2 Image Menu

The Image menu pops up if the "Image" button in the menu bar is pressed or if "Alt+I" is pressed while the pointer is in the main window. The choices in the menu allow for opening additional windows or accessing special functions:

Table 2: The "Image" menu

Menu Menu Choice Shortcut Description
Image: Image Menu Open Ctrl+o Pops up "File"-window
Colors Ctrl+c Pops up "Colors"-window
Close F1 Takes away "Display"-window
Show resolution rings Ctrl+r Toggle display of resolution rings
Hide statistics Ctrl+a Toggle display of some image info in lower left corner
Keep view Ctrl+v Keep same aspect of image and color scheme when loading new images.
By default, image colors are recomputed and images are shown to fit in the window
Keep colors Ctrl+k Keep same color scheme when loading new images
Reset colors Ctrl+t Recomputes best color scheme for loaded image
Show 3D Ctrl+d Toggle display of 3-D plots of zoomed areas (for zoom factors > 4)
Next image Ctrl+n Load image with image number increased by 1 unit
Previous image Ctrl+p Load image with image number decreased by 1 unit
Integrate Ctrl+i Integrate the contents of the zoomed area and show results in upper right corner
Zoom options   See "Zoom Options" submenu

The choices in the "Zoom Options" submenu affect the way the image looks at zoom factors < 1.0. If one pixel on the monitor corresponds to more than 1 pixel (N pixels) in the image, image colors can be calculated in several ways. Please note, that "N'th" pixel mode is faster than others since it doesn't involve computation.

Table 3: The "Zoom Options" submenu

Menu Menu Choice Description
Display: Zoom Options Menu N,th pixel Use every N'th pixel to display colors and ignore others
Average pixels Take average value out of N pixel to display colors
Maximum pixels Take maximum of N pixel to display colors


3.3 Toolbox

The toolbox on the left hand side of the "Display"-window features the following functions:

Table 4: The "Image Toolbox"

Toolbox Symbol Description
Display: Image Toolbox: Previous image Load previous image
Toolbox: Next image Load next image
Toolbox: Stop Stop loading images (see next)
Toolbox: Forward Continuously load images by increasing image number
Toolbox: Entire image Display entire image
Toolbox: Zoom in Zoom in
Toolbox: Zoom out Zoom out
Toolbox: Max. scale Upper limit for distributing grey scales
Toolbox: Min. scale Lower limit for distributing grey scales


3.4 Image Area

3.4.2 Mouse Button Functions

Within the image area of the "Display"-window the mouse buttons have the following functions:


3.4.3 Information Areas

In the corners of the image area of the "Display"-window certain information will be displayed, depending on previous actions:


3.5 "File" Window

File Window


The "File"-window can be accessed by selecting the corresponding choice in the "Windows"-menu or by pressing the "Ctrl+f"-key while the pointer is in the display window. This window is used to manually load images.

When the window pops up, the contents of the current working directory are listed in the file area of the window. By double-clicking a file, the corresponding file will be loaded. A single click will transfer the string of the selected file to the "Selected File:" area of the window and you will have to press the "Load"-button to actually load the image. By pressing the "List"-button, the directory is searched and files matching the "Search Pattern" are listed. By pressing the "Follow"-button a series of image files will be loaded. Image numbers will be continuously increased.


3.6 "Colors" Window

Colors Window


The "Colors"-window can be accessed by selecting the corresponding choice in the "Windows"-menu or by pressing the "Ctrl+c"-key while the pointer is in the display window. This window is used to manipulate image colors.

The continuous red line in the plot shows the frequency of certain pixel values in the entire image, i.e. an intensity histogram. The maximum frequency is normally something like the average background or the "most probable" pixel value. In the histogram, two dashed bars mark the Min and Max values. To change Min or Max, enter values in the corresponding fields (and press RETURN!) or move the left or right bar using the left or right mouse button, respectively, and wait a moment until the image is rescaled accordingly.

When loading an image, the program automatically distributes grey scales in equidistant intensity bins between a minimum (Min) and maximum (Max) value. All pixel values > Max are drawn in black and all values < Min in white. Min usually is 0, but Max is calculated such that 99.998 % of all pixels in the image have intensities <= Max. The Max and Min can be entered in the upper part of the "Colors"-window or in the upper (Max) and lower text (Min) text field of the toolbox in the "Display"-window.


3.7 3-D Plot

3-D plot


A 3-D representation of a portion of the image can be obtained by selecting the "Turn ON 3-D plot"-choice in the "Options"-menu or by pressing the "Ctrl+d"-key while the pointer is in the display window. This option works at zoom factors > 4 only. It dumps some statistics of the displayed area in the upper left corner of the display area. The aspect of the peak to be display may be altered by entering a minimum or maximum threshold in the corresponding fields of the vertical axis. As in the regular image area, the right mouse button may be used to recenter the peak. This is a little bit of trial and error but once you get used to it, it works. You may switch between 3-D and regular display any time by pressing Ctrl+d.


3.8 "Cross-section" Window

Cross-section Window


A cross-section through a portion of the image can be obtained by dragging the left mouse button in the image area of the "Display"-window. The window features the following elements:

Table 1: The "Cross-section"-Window

Element Description
No. of peaks Specifies the number of peaks between two dashed lines in the plot area of the window.
Use the arrow buttons on the right hand side of the fextfield to increment or decrement the value by 1.
When pressed, the real space cell constant is calculated from the distance between the two dashed lines and the number of peaks. The result is displayed in the message area.
Message area Shows the coordinates of the start and end of the line, the angle with the base line, maximum, minimum, average and standard deviation of the intensities along the drawn line. When changing the no. of peaks manually, the second line displays the derived cell constant.
Plot: vertical axis Interpolated intensities
Plot: upper horizontal axis Length of line in pixel units
Plot: lower horizontal axis Length of line in mm units
Plot: left dashed line Marks the beginning of a measured distance.
This line can be moved using the left mouse button.
Plot: right dashed line Marks the end of a measured distance.
This line can be moved using the right mouse button.
Plot: horizontal red lines Show the total length of the line in pixels (mm) and the distance between the dashed vertical lines.

The pointer can be used to measure distances by setting the red dashed lines to the desired position along the drawn line. This is particularly useful if you want to measure cell constants. The program features a peak finding algorithm which tries to set the bars on top of the first and the last peak of the plot. Inbetween the peaks the program then looks for other peaks and tries to calculate the best inter-peak distances by assuming a harmonic oscillation. The no. of peaks calculated by the program is displayed in the "No. of peaks" textfield. Of course, this value can be modified. The derived cell constants do not take into account any particular setting or symmetry of the crystal but calculates cell constants assuming plain orthogonal axes.