When analyzing hyperspectral image data you might encounter situations when you would like to save the data of a particular image for later processing. ImageLab provides such an auxiliary image data space in the form of an image repository, the images of which are displayed on individual tabs of the 2D Imager. There are three ways to put image data into the image repository:
- Clicking the "add to image repository" button: . All of the built-in multivariate analysis tools offer this button (if appropriate), clicking it transfers the corresponding image data into the special image repository and displays the resulting image on an additional tab of the 2D Imager.
- Calculating one of the predefined special images (see below).
- Using the script command AddImgToRepository
Predefined special Images
Apart from displaying spectra and the corresponding images, ImageLab provides a few additional special purpose images:
- Total intensity map: this plot shows the integral of the spectrum of each pixel. It is, by default, displayed in black and white; high values (light gray to white) indicate high concentrations. Please note that the total intensity plot should be applied to baseline corrected spectra only. The total intensity plot can be created by clicking the button in the 2D Imager (see figure below).
- Variance map: shows the variance of the spectrum of each pixel. It is displayed using the color palette "MorgenStemning", by default. The variance plot can be created by clicking the button in the 2D Imager (see figure below).
- Maximum map: visualizes the maximum of the spectrum of each pixel. It is displayed in brown/red color tones, by default. The maximum map can be created by clicking the button in the 2D Imager (see figure below).
- Minimum map: visualizes the minimum of the spectrum of each pixel. It is displayed in blue shades, by default. The minimum map can be created by clicking the button in the 2D Imager (see figure below).
- Suspicious pixels: indicates various kinds of problematic pixels; see the section on suspicious pixels for details.
- Chemical map: displays arbitrary user-defined chemical maps. Chemical maps can calculated by clicking the button in the 2D Imager (see figure below).
- Time Delay Map: displays the shift along the (time) axis of pulsed signals. See the description of the Time Delay Map for details.
||The total intensity plot, the variance and the min/max maps are prepared to be executed in parallel on multi-core processors. The increase in speed corresponds roughly to the number of CPU cores in your system (a four core system will be faster by a factor of 4). You can fine-tune the assigned processing power in the preferences of the program (see the option Allowed CPU Usage in Multiprocessor Systems).
Restricting the spectral range
The total intensity, the variance, the minimum and the maximum map can be restricted to a certain spectral range by right clicking the corresponding buttons. This feature may be useful if the spectra show a high intensity peak of no analytical value (i.e. a peak caused by the excitation laser in Raman spectroscopy). The range restriction is applied to all subsequent plots until you remove the restriction.
||Simply click the corresponding button in the 2D Imager and enter the parameters (if required). The analysis of suspicious pixels and the calculation of time delay maps can be started from the main menu (choose Preprocessing/Detect Suspicious Pixels or Image Analysis/Special Images/Time Delay Map).