Viewing Very Large Images (VLIs)
For images or image sets opened with sub-resolution data available, Image-Pro provides the Very Large Image (VLI) viewer. It is designed to let you view and analyze very large images that would otherwise, due to computer processing resource limitations, be too large to work with in the normal Image-Pro workspace. The VLI viewer only works with file formats that provide image data at multiple resolutions. When such images or image sets are opened, if each frame will consume too much memory at full resolution Image-Pro will automatically open it into the VLI workspace. Images with too-large frames from file formats that do not support multiple resolutions will fail to load with a error message indicating why.
By default, multiresolution images or image sets with frames smaller than a threshold size will open into a normal workspace. This frame-size threshold is set by the File Image Loading Very Large Image Viewer Threshold option, which is 20% of free image memory by default. Since the threshold depends on free memory, sometimes the same file may open into the VLI workspace and at other times may open into a normal workspace. To prevent this uncertainty you could adjust the VLI threshold to a higher value so all of your images open into a normal workspace or to a lower level so they all open into the VLI workspace. Or you can enable the File Image Loading Multiresolution Images Below Threshold Load as Very Large Image option. If checked, this option will force even very small multresolution images to open in the VLI workspace.
The VLI viewer supports the features listed below. Other image processing features of Image-Pro are disabled in the VLI viewer.
- Status bar updates of the X/Y location and the intensity under the cursor.
- Normal zoom, pan, and scroll operations.
- Local Zoom.
- For image sets with VLI frames the normal image set navigation bar will show, but neither the Color Composite panel nor any of the 3D viewer options will be avaliable.
- Annotation and other simple overlays (like the active data overlay).
- Display group controls for brightness, contrast, and gamma adjustment.
- Image information and image properties displays.
- Most manual measurements (but without supporting automated features, such as "snap to edge", trace and magic wand). Some measurements that you might typically be able to get from the manual measurement features will not be possible with VLIs (like Density/Intensity).
- Definition of a new type of ROI, and extraction
of that ROI to a normal image in memory on which all normal image-based
features will work fine. Only a single rectangular ROI can be created on VLI image workspaces.
VLI Ribbon
When the Very Large Image (VLI) viewer is active, in place of the normal Image Tools context ribbon, a Large Image Tools context ribbon will be available. All of the enabled controls are identical to the same controls in the Image ribbon. Controls for functions that are not available in the VLI workspace will be missing or disabled.
VLI Tools
Using the Regions of Interest tools on the ribbon and the VLI Tools floating on the image, you can create a ROI on the image and extract that into a normal workspace to analyze or process the extracted portion of the VLI. You can extract a ROI at full-resolution or the whole image at a sub-resolution (or a combination of the two) so long as the extracted image data does not consume too much memory. VLI image sets may have multiple channels and/or multiple Z positions. You can use the selection sliders or Ctrl-Click on individual set locations to select only a portion of the image set's frames to be extracted into a new image set.
The Extract button extracts the selected portion of the image or image set to a new, normal workspace. For extractions from a single-frame VLI image, the extracted ROIs or sub-resolution whole-images will accumulate with an experiment display showing where each extraction came from in the image and listing basic data about each extraction.
The Resolution slider selects the sub-sampling resolution to use, or the size ratio of each extracted pixel to each full-resolution pixel. The resolutions available are only those that the file format supplied for the displayed image or image set.
The Emphasis switch allows you to select whether Image-Pro should emphasize preserving the size ratio (by auto-adjusting the size of the ROI), or preserving the region of interest (by auto-adjusting the resolution/size ratio) in order to keep the extracted image data to a limit.
The Limit to slider lets you set the percentage limit of the available image memory for which an extract is allowed to consume. This could be set to 80-90% if only one copy of the extracted image data is needed, or may need to be 10-20% if multiple simultaneous copies of the image data are needed for processing. This is the memory limit that is used during the computations the tool uses to auto-adjust either the resolution or the ROI.
The memory usage bar will graphically display the percentage of the specified memory limit that would actually be used when extracting an image with the current combination of the image ROI and the selected resolution.