-
Akarsh Simha authored
1. Moved KSUtils::getDSSURL() to KSDssDownloader::getDSSURL() with expanded, but backward-compatible options. 2. Created a new class KSDssImage to load and hold a DSS Image as a QImage along with a metadata structure. The metadata struct is designed to supplement information about the DSS image (eg: size in arcminutes, center RA/Dec, photometric band, generation of DSS etc.) 3. Created a new class KSDssDownloader which completely takes care of downloading DSS images given a SkyPoint and a destination file. It: - Formats the URL - Sets up a download job - Tries alternate versions if the download failed - Writes the file along with metadata as a compressed PNG image 4. Employed this new machinery in ObservingList 5. Regression: partial removal of (anyway broken) SDSS support Motivation: + DSS images are heavily used by visual astronomers to compare what they see in the eyepiece with imagery. These are far superior to "photoshopped" / HDR-ed astrophotographs since the brightness is roughly a real measure of brightness. + Visual astronomers prefer blue images to red images since they closer approximate what may be seen with the eye. However, sometimes, blue images are not available, so it is inevitable to fall back to red. In these times, it is important to know what plate is being looked at (blue or red) + We intend to eventually be able to overlay DSS images on the sky map. A system for caching and rendering compressed (PNG as opposed to FITS) DSS images may be important, and this requires proper metadata. Solutions: + KSDssImage ensures that image and metadata are kept together. The width and height are important meta data for any DSS image. While these could be figured using a pixels/arcminute ratio, this ratio is not the same across various generations of the DSS. + KSDssDownloader goes through a sequence of attempts at downloading DSS images in an order that is set by us, rather then set by the MAST website (which would be the case if we did not specify which version we want). The MAST website prefers POSS II Red > POSS II Blue > POSS I Red etc. whereas we would want to prefer POSS II Blue > POSS II Red > ...; More powerfully, this sequence may be a configurable option later. The other advantage of doing this sequence, instead of letting the DSS search find a version for us, is that of knowing what we've got. The gif from MAST website has no metadata in it (although GIF does support metadata). This means we don't know which version of the survey we got. + Test cases: Palomar 6 is an interesting test case because POSS II blue plate is unavailable. The script figures out that the blue plate failed, and fetches the red plate instead. The advantage of KSDssDownloader is that we now know that we are holding a red plate -- it's in the PNG metadata. Future: + Need to expand to SDSS. Then, allow for proper detection of whether the coordinates fell in SDSS footprint or not. Then, use the same falling-through to fall-back to DSS after SDSS. + Ability to compose a closest approximation to visual view from R/B plates + DSSimage SkyComponent that holds multiple DSS Images along with their respective coordinates. CCMAIL: kstars-devel@kde.org
b3d24661