extentspythonqgisqgis-plugins
I try to make plugin in QGIS that compare 2 bounding box data, ex:
(-32.61442167739459, -32.017601026186576, 13.015663782506067, 13.428145228091406)
and
(-38.6102467739459, -38.017601026186576, 33.01563382506067, 33.624945228091406)
and want to picture it in a square or polygon like shape.
Does QGIS have a module in Plugin that can do such a thing?
The following little Python function will output the bounding box coordinates of the currently active feature:
def printBB():
feature = iface.activeLayer().selectedFeatures()[0]
print feature.geometry().boundingBox().toString()
To define the function, open the Python console from the Plugins menu, copy and paste the three lines into the console, and press enter. Then you can call the function by typing printBB() and pressing enter while the desired feature is selected.
Edit: For newer Python versions (Python 3.x) use this (print() with brackets):
def printBB():
feature = iface.activeLayer().selectedFeatures()[0]
print(feature.geometry().boundingBox().toString())
I would use gdal_translate http://www.gdal.org/gdal_translate.html with Virtual raster (.VRT) output http://www.gdal.org/gdal_vrttut.html as an interim format.
gdal_translate -of VRT -projwin ulx uly lrx lry input.png output.vrt
Place the upper left and lower right coordinates of the bounding box as -projwin values. Notice the order which is different from BBOX which is lower left, upper right.
Now you can use the output.vrt file as input for gdal2tiles. Advantage in using VRT instead of GeoTIFF or any other image format as an interim format is that VRT is just a short XML file and no image data are copied.
Edit
You approach by attaching georeferencing into .VRT file with -a_ullr and converting VRT into tiles is right. With a little bit different command the result looks good. Actually the commands can be as simple as these:
gdal_translate -of VRT -a_srs EPSG:4326 -a_ullr 112 24 115 21 img.png output.vrt
gdal2tiles.py output.vrt
The directory "output" contains Leaflet, OpenLayers, and Googlemaps maps. The leaflet.html one looks like this:
You may not really want to create zoom levels -z 0-4 because level zero covers the whole world and the footprint of your image is rather small. Automatically created map contains zoom levels 6-10 which suit with the size of your image better. That option -p raster does not create Leaflet and Googlemaps page may be a bug in gdal2tiles.py.
Best Answer
Yes, it's the QuickWKT plugin (WKT = "Well-Known Text"). The bounding box would be treated as a polygon, and WKT would look like:
Note that any polygon shape is possible, but coordinates following this model will generate a rectangle, which is what you want for a bounding box. You can't get away specifying only two corners, as you have in the question, you have to specify all four corners, and the first and last coordinates have to be the same. That's how WKT indicates that the polygon is closed.
A screenshot with the WKT for your first example: