GetMap Geoserver Width and Height

Question

I was wondering how to avoid the Geoserver transformation that takes place once you request an image via GetMap by using image/geotiff at the end of the url sentence in the browser.

I am experimenting with a geotiff that has 300 x 300 pixels (290 KB) in the server.

If I set the parameters in the GetMap request (url):width=1012&height=1012 The output image will have 1012 x 1012 pixels (1,002 KB). If I request width=300&height=300 - as in the original - the output image will have 300 x 300 pixels and 290 KB.

If I overlap the two images, both have the same bounding rectangle but obviously the pixels don´t match, understood.

But the most intriguing and worrying thing is that if we analyze these 2 output images by using gdalinfo -stats in the command line, you will see that the 1012x1012 image has its parameters totally wrong (Minimum, Maximum, Mean, etc.) but the 300x300 one too.

In fact the original image is a Float32 raster and the 2 output ones are type Byte.

Is there any way of getting the original one from Geoserver, via url, without any transformation at all?

Answer 1

When you make a WMS request you are asking for a picture of your data. The output is determined by the style you request (via the SLD you provide or the default). This is why the statistics are different for the the two files you request. Since the returned images are simply colours they can be stored in 3 bands of Byte - there is simply no need to use the Float values.

If you want to use the data values of the imagery then you need to make a WCS request which is like a WFS request (but for rasters) in that it returns the actual data not the picture of the map.