Re: [Qgis-user] Georeference png files
Hi Nick, Thanks for this method. I didn't manage to do it in the QGIS python console but I installed gdal on the mac and it does the job perfectly. I have more than to make a script to convert the whole and I could exploit that on QGIS. > Le 22 déc. 2019 à 21:06, Nick Hopton a écrit : > > It is possible to assign georeferenced bounds to a raster using > gdal_translate: > > gdal_translate -a_ullr input.png output.tiff > > Where: > = upper left x > = upper left y > = lower right x > = lower right y > > The resulting tiff won't contain CRS data. > > Nick. > > > > > -- > Sent from: http://osgeo-org.1560.x6.nabble.com/QGIS-User-f4125267.html > ___ > Qgis-user mailing list > Qgis-user@lists.osgeo.org > List info: https://lists.osgeo.org/mailman/listinfo/qgis-user > Unsubscribe: https://lists.osgeo.org/mailman/listinfo/qgis-user ___ Qgis-user mailing list Qgis-user@lists.osgeo.org List info: https://lists.osgeo.org/mailman/listinfo/qgis-user Unsubscribe: https://lists.osgeo.org/mailman/listinfo/qgis-user
Re: [Qgis-user] Georeference png files
It is possible to assign georeferenced bounds to a raster using gdal_translate: gdal_translate -a_ullr input.png output.tiff Where: = upper left x = upper left y = lower right x = lower right y The resulting tiff won't contain CRS data. Nick. -- Sent from: http://osgeo-org.1560.x6.nabble.com/QGIS-User-f4125267.html ___ Qgis-user mailing list Qgis-user@lists.osgeo.org List info: https://lists.osgeo.org/mailman/listinfo/qgis-user Unsubscribe: https://lists.osgeo.org/mailman/listinfo/qgis-user
Re: [Qgis-user] Georeference png files
@Nicolas : I tried to save it in .geoTiff format (right click, export, save as) I end up with a white or black tile … 😕 If you want to try, here is the png and the coordinates (if you get there, I would like to know the method) [cid:FA974430-F7BF-4AD9-BC9D-316070788235] N = 71,71875 W = -180 S = 71,3671875 E = -179,6484375 @ Paolo & @ Nicolas : Thanks, I will try the method with the .pngw file (without being mistaken in the calculation) ___ Qgis-user mailing list Qgis-user@lists.osgeo.org List info: https://lists.osgeo.org/mailman/listinfo/qgis-user Unsubscribe: https://lists.osgeo.org/mailman/listinfo/qgis-user
Re: [Qgis-user] Georeference png files
You can use a pngw. Try saving your map as an image for an example. Cheers. On 22 December 2019 17:52:10 EET, Nicolas Cadieux wrote: >Hi, > >To my knowledge, and I may be wrong, you cannot insert a geotag in a >.png. Try saving as .tif. That should be georeferenced. If you >absolutely want to use a .png, you will need to create a world file. >To see how they work, just export the map window using .png. A world >file will be created and will contain the information you are looking >for. The world file is a text file that can be opened with notepad++ >or any text editor. > >https://en.wikipedia.org/wiki/World_file > >Nicolas > >> Le 22 déc. 2019 à 10:16, LE LAMER Romain a >écrit : >> >> Hi, >> I have a complete map in tiles of 256 x 256 px in png format not >georeferenced. (if I open them in QGIS they are superimposed on each >other) >> 1024 tiles in Longitude and 512 tiles in Latitude = 524288 tiles. >> Each tile is named as follows: map_Z_X_Y.png >> Z => zoom (11). >> X => from 0 to 1023. >> Y => from 0 to 511. >> >> # If I say no nonsense, I can, by calculation, know the Longitude and >Latitude: >> lonN = (360 * (X / 1024)) - 180. >> latW = 90 - (180 * (Y / 512)). >> >> In the same principle, I can determine the South East coordinates. >> I know that the whole map is divided into 1024 tiles of 256px in >longitude, 1024 x 256 = 262144px for 360 ° so a tile = (256 x 360) / >262144 = 0.3515625 ° >> Same reflection for the latitude, 512 tiles of 256px or 512 x 256 = >131 072px for 180 ° so a tile = (256 x 180) / 131 072 = 0.3515625 ° >> >> lonE = lonN + 0.3515625 >> latS = latW - 0.3515625 >> >> How can I add these coordinates to the png file? >> >> Thanks >> ___ >> Qgis-user mailing list >> Qgis-user@lists.osgeo.org >> List info: https://lists.osgeo.org/mailman/listinfo/qgis-user >> Unsubscribe: https://lists.osgeo.org/mailman/listinfo/qgis-user -- Please excuse my brevity.___ Qgis-user mailing list Qgis-user@lists.osgeo.org List info: https://lists.osgeo.org/mailman/listinfo/qgis-user Unsubscribe: https://lists.osgeo.org/mailman/listinfo/qgis-user
Re: [Qgis-user] Georeference png files
Hi, To my knowledge, and I may be wrong, you cannot insert a geotag in a .png. Try saving as .tif. That should be georeferenced. If you absolutely want to use a .png, you will need to create a world file. To see how they work, just export the map window using .png. A world file will be created and will contain the information you are looking for. The world file is a text file that can be opened with notepad++ or any text editor. https://en.wikipedia.org/wiki/World_file Nicolas > Le 22 déc. 2019 à 10:16, LE LAMER Romain a écrit : > > Hi, > I have a complete map in tiles of 256 x 256 px in png format not > georeferenced. (if I open them in QGIS they are superimposed on each other) > 1024 tiles in Longitude and 512 tiles in Latitude = 524288 tiles. > Each tile is named as follows: map_Z_X_Y.png > Z => zoom (11). > X => from 0 to 1023. > Y => from 0 to 511. > > # If I say no nonsense, I can, by calculation, know the Longitude and > Latitude: > lonN = (360 * (X / 1024)) - 180. > latW = 90 - (180 * (Y / 512)). > > In the same principle, I can determine the South East coordinates. > I know that the whole map is divided into 1024 tiles of 256px in longitude, > 1024 x 256 = 262144px for 360 ° so a tile = (256 x 360) / 262144 = 0.3515625 ° > Same reflection for the latitude, 512 tiles of 256px or 512 x 256 = 131 072px > for 180 ° so a tile = (256 x 180) / 131 072 = 0.3515625 ° > > lonE = lonN + 0.3515625 > latS = latW - 0.3515625 > > How can I add these coordinates to the png file? > > Thanks > ___ > Qgis-user mailing list > Qgis-user@lists.osgeo.org > List info: https://lists.osgeo.org/mailman/listinfo/qgis-user > Unsubscribe: https://lists.osgeo.org/mailman/listinfo/qgis-user ___ Qgis-user mailing list Qgis-user@lists.osgeo.org List info: https://lists.osgeo.org/mailman/listinfo/qgis-user Unsubscribe: https://lists.osgeo.org/mailman/listinfo/qgis-user
[Qgis-user] Georeference png files
Hi, I have a complete map in tiles of 256 x 256 px in png format not georeferenced. (if I open them in QGIS they are superimposed on each other) 1024 tiles in Longitude and 512 tiles in Latitude = 524288 tiles. Each tile is named as follows: map_Z_X_Y.png Z => zoom (11). X => from 0 to 1023. Y => from 0 to 511. # If I say no nonsense, I can, by calculation, know the Longitude and Latitude: lonN = (360 * (X / 1024)) - 180. latW = 90 - (180 * (Y / 512)). In the same principle, I can determine the South East coordinates. I know that the whole map is divided into 1024 tiles of 256px in longitude, 1024 x 256 = 262144px for 360 ° so a tile = (256 x 360) / 262144 = 0.3515625 ° Same reflection for the latitude, 512 tiles of 256px or 512 x 256 = 131 072px for 180 ° so a tile = (256 x 180) / 131 072 = 0.3515625 ° lonE = lonN + 0.3515625 latS = latW - 0.3515625 How can I add these coordinates to the png file? Thanks ___ Qgis-user mailing list Qgis-user@lists.osgeo.org List info: https://lists.osgeo.org/mailman/listinfo/qgis-user Unsubscribe: https://lists.osgeo.org/mailman/listinfo/qgis-user
