Krishna, Can you share a bit more about the raster image source file? How discrete are the colors?
If there are only a few colors, then this workflow may meet the need, however kludged it may be. See if this approach helps... it worked for me with only a few colors... with more than a few, it would almost certainly fail. Step 0 - determine how unique the colors are that you're working from...and how many there are. Step 1 - take core RGB raster and split into three greyscale images... keep dimensions the same as the original and duplicate the world files for the core RGB raster so there's also a world file for each channel. Step 2 - import the three greyscale images into QGIS. Step 3 = In Raster Calculator [1] extract each single R, G, xor B unique color value of interest into an output image Step 4 - Use Polygonize [2] on the output from step 3 ... AND also using Step # 3's output as a Screen under Polygonize's advanced options. Step 5 - apply the unique colors to the output. Step 6 - Save the output shape file. Repeat as needed. This approach worked sufficiently well to take LIDAR-generated raster vegetation base maps from the mapping software OCAD [3] and convert those raster images to shape files for returning to OCAD as vectors and assignment to vegetation types. Those shape files do get big... and over any substantive area, I can easily end up with > 150 K shapes in each file. I set up a presentation file showing the approach using the QGIS graphical modeler [4] in a shared Google Drive, if you want to look it over. Shortfalls and work arounds:: theoretically, I **think** the raster calculator should work on the original RGB source file, but I could never get it to work, so I tried the decompose-and-reassemble approach ...and it did work. ...and being lazy and busy, once I found a working approach I kept using it. I'm sure it could be improved, but I don't use it often enough to warrant a hard scrub for optimization... and there are lots of other things to do while the graphical modeler runs through the hoops. [1] Raster Calculator documentation page: https://docs.qgis.org/3.16/en/docs/user_manual/working_with_raster/raster_analysis.html#raster-calculator [2] Polygonize documentation page: https://docs.qgis.org/3.16/en/docs/user_manual/processing_algs/gdal/rasterconversion.html?highlight=polygonize#polygonize-raster-to-vector [3] OCAD Home Page https://www.ocad.com/en/ [3] My efforts at creating shapes from rasters Filename: Creating_shapes_007.pdf https://drive.google.com/drive/folders/1y7OKQM3XNqrTMFEgj8YM5-4WSY0CAQnl?usp=sharing Hope this helps. All my best, Craig [Message trimmed] > > > Today's Topics: > > 1. Re: Raster to Vector without losing the symbology (Andy Harfoot) > > > ---------------------------------------------------------------------- > > Message: 1 > Date: Mon, 19 Jul 2021 14:40:06 +0100 > From: Andy Harfoot <a...@geodata.soton.ac.uk> > To: qgis-user@lists.osgeo.org > Subject: Re: [Qgis-user] Raster to Vector without losing the symbology > > Or extract the three bands into three separate vector files and then > union the three together to get the unique combinations of RGB values. > > Cheers, > > Andy > > > >> Le 18 juill. 2021 ? 12:51, krishna Ayyala <ayyalakris...@gmail.com> a > >> ?crit?: > >> > >> ? > >> I have an image on my qgis map that has 3 bands. Band1 (red), > >> Band2(green) and Band3(blue). This image has different?colors.Is it > >> possible to convert this image into a vector?which should look > >> exactly like the image. > >> > >> That means; Is it possible to have the vector file that should?have > >> the same colors as that of the image. > >> > >> Regards. _______________________________________________ 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