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5. Cloud Image Viewer

5.1 Cloud Image Viewer Application

The Cloud Image Viewer application is an applet that selectively displays images of point cloud scans. For that purpose, 6 static camera angles have been chosen, and snapshots of each point cloud scan have been taken with EvalViewer. The scans have been color coded for some visual enhancement.

The interface is divided into 3 components:

  1. Image Selector: along the left side of the interface, the user may select individual images for display
  2. Image Display: the largest area of the interface is occupied by the image display, which displays single images and composited images
  3. Toolbar: along the bottom of the interface, the user may control the behavior of the application and the displayed images

Figure 1.15: Cloud Image Viewer Interface
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5.1.1 Toolbar

Information Tab: Displays current state (Ready or Working), and other information about the application's current status, e.g. Compositing x/n, or Redrawing, etc.

List Tab: Dictates whether the image selection list is displayed in a sectioned (topological) fashion, or in a numerical order.

Camera Tab: Selects one of six pre-defined camera viewpoints.

Select Tab: Convenient way of selecting all, none of the images in the list, and inverting the current selection (selected->not selected and not-selected->selected).

Permutation Tab: Refers to the permutability of the selected scans throughout different camera viewpoints. Once the camera viewpoint is changed, the list of scans can either be cleared (de-select all), the list can be updated (linked) to reflect all selected scans from the previous camera viewpoint, or the list of selected scans for each different camera viewpoint can be kept independently. For the option "link" it is important to note that only those images are kept selected that exist in the new camera viewpoint.

Redraw Tab: Redrawing and compositing images is an intesive CPU operation and does take time. The user may choose to redraw/composite the displayed image either automatically after any change takes place (e.g. select/de-select a scan), or manually upon request.

Composition Tab: The method of composition refers to the way overlapping pixels are composited; overlapping pixel colors can be added (transparency), overwritten (opaque last), or discarded (opaque first). The displayed image is produced by compositing the selected images from the list in order from top to bottom. To that end, the pixels from each selected image are copied into the final image. In the process of copying the pixels, Opaque First and Opaque Last dictate whether to overwrite or discard pixels depending on whether a pixel from a previous source image has already occupied the (x,y) coordinate of the composited image.

Background Tab: Specifies a custom background color for the composited image; the background color appears in place for all fully transparent pixels.

Figure 1.16: Compositing Images (Information Tab)
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Figure 1.17: Custom background color (Background Tab)
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