Image Display Functional Requirements

Software Requirements

Overview

The size and complexity of the full mosaic (8K x 8K pixels, 8 CCDs) present several problems not encountered by existing images and displays. For the purpose of displaying DEIMOS images, we propose two display windows, each running on its own dedicated monitor at the telescope. One will be used to display the full image (block-averaged or subsampled), which will serve the function currently handled by the "panner box"; we will calll this the "full-image display." The second monitor (which we refer to as the "work display") will handle the functions currently handled by the main display of various display tools. With DEIMOS, however, it will rarely -- if ever -- display any more than a small portion of the entire mosaic, as it will normally display at full pixel or magnified scales.

These general rules apply:

Built-in analysis functions are described under Quick-Look Requirements.

Nomenclature

An image (or frame) is read into shared memory by the image display -- or other -- process. From here, the image display writes it into an effective video memory using a specified transfer function to perform an intensity transformation or mapping. The transfer function can be described by both a form (eg, linear, log, sqrt) and limiting values (minimum and maximum values outside of which the intensities are effectively floor-ed and ceiling-ed with the limiting values). Once in the effective video memory, the actual mapping of intensity values into specific grey levels or colors on the screen (ie, control of the gun voltages) is under the control of a look-up table (LUT). The user adjusts the contrast and brightness levels by changing the LUT.

An image plane refers to a section of the effective video memory which is treated as a single image. Blinking alternates between image planes.

An autoscaling algorithm will automatically compute limits (and potentially the form) of the transfer function.

Specific Requirements

Design Notes

The transfer function control could be implemented fairly easily. There will be a pull-down menu of forms -- linear, log, etc. There will be (always displayed) two text boxes for the limits, ie, minimum and maximum. These limits are either typed in the box by the user, or -- most commonly -- provided by the autoscaling algorithm. There will also be a pair of radio buttons, "auto" and "fixed", for selecting between the automatic algorithm or user-forced values. These latter can be specified by the user, or the current values simply "locked" in. There should also be a "redisplay" button, for applying any modifications to the min/max limits or forms. The appearance matching is selected by a third button. The user drags out a box around the region of interest, and clicks on the "match appearance" button. The pixel values within the boxed region in each image are compared, and the transfer function for the second image is derived from the transfer function for the first image combined with the scaling and offset values from the comparison of the two images. The second image is redisplayed with the new transfer function values.

The highly-interactive limits selection would be chosen by another button. In this case, the user drags out a box around the image region of interest. This selected region is then reloaded into video memory with a transfer function running from the minimum to maximum intensity encompassed by the box, and the LUT is reset to full ramp. The user will then adjust the LUT (via standard mouse control) to bracket the intensities of interest. When ready, the user selects this range (either by another mouse button or a graphical button), and the LUT ramp is mapped backwards to estimate the min and max value of interest to the user. These values become the new transfer function limits, the boxed region is redisplayed (using the new limits) and the LUT ramp is reset to full range. This procedure is repeated until the user selects the "redisplay" button, when the (final) transfer function limits are applied to the entire image. Note that an "undo" option, to reverse the last change, will probably be required.

Hardware Requirements

Two dedicated monitors will be required. We prefer at least one 2K x 2K monitor for the "full image" display; however, the current cost of these monitors is very high. Therefore, the system must work with two 1K x 1K monitors.

8-bit display grayscales or colors are probably adequate, but we should allow for the possibility of 24-bit display.

Three (?) button mouse.

Lots of memory (TBD).


Last modified: 07 Mar 96
phillips@ucolick.org