raster export with non-usual RGB values

[riccardoklinger]

I have received a tiff file with DEM-values (file: https://www.dropbox.com/s/adfa62i6rcbhd9w/mdt_clipped.tif?dl=0) which are more or less higher than 255... when it exports it treats each value as RGB-values which results in this:

when saved as a new file with check "save as shown" and exported using the plugin it shows well on the screen:

this alsco counts for values below 1 in the raster image and non-integer values.
the line that does the storage is:
if str(i.dataProvider().metadata()[0:4]) == 'JPEG' and str(i.crs().authid()) == 'EPSG:4326':
shutil.copyfile(in_raster+".aux.xml", out_raster + ".aux.xml")
shutil.copyfile(in_raster, out_raster)
else:
processing.runalg("gdalogr:warpreproject",str(in_raster),str(i.crs().authid()),"EPSG:4326",0,1,"",prov_raster)
format = "jpeg"
driver = gdal.GetDriverByName( format )
src_ds = gdal.Open(prov_raster)
dst_ds = driver.CreateCopy( out_raster, src_ds, 0 )
dst_ds = None #free the dataset
src_ds = None #free the dataset

[tomchadwin]

So to handle this, we need to do two things:

1. Detect when rasters are not plain RGBs - presumably by looking at the band render type, and I'm not sure how to get to that in the API
2. Find out how to "Save raster layer as rendered image" via the API, which I also don't know how to do

[tomchadwin]

1 is rasterlayer.rasterType(), which returns:

GrayOrUndefined
Palette
Multiband
ColorLayer

[riccardoklinger]

I'll close #133 and paste the last comment here as this one is vital:

Use gdalwarp to transform the original coordinates to EPSG:4326 the standard for leaflet in a temporary file, for example:
gdalwarp -s_srs EPSG:2100 -t_srs EPSG:4326 -r bilinear " + filename +".tif " + filename + ".tiff"

Use gdal_translate to convert the temporary file to PNG:
gdal_translate -of PNG -scale " + filename + ".tiff " + filename + ".png"
A nice touch would be an option to automatically convert black or white to transparent for scanned images that have no alpha channel.

Get the coordinates from the PNG file:
ds = gdal.Open(filename+".png")
width = ds.RasterXSize
height = ds.RasterYSize
gt = ds.GetGeoTransform()
minx = gt[0]
miny = gt[3] + widthgt[4] + heightgt[5]
maxx = gt[0] + widthgt[1] + heightgt[2]
maxy = gt[3]
tmp = "["+str(miny)+","+str(minx)+"],["+str(maxy)+","+str(maxx)+"]"
ds = None

Delete the temporary TIFF file.

Repeat for next graphic.

[riccardoklinger]

there seems no easy way to save a raster as rendered via the API ATM. I added a hint in the instruction to do this by hand.

[tomchadwin]

I wonder if Nathan's qgis2img achieves this: https://github.com/DMS-Aus/qgis2img

[tomchadwin]

I also got an answer on StackExchange:

http://gis.stackexchange.com/questions/68803/qgis-save-raster-as-rendered-image?noredirect=1#comment207705_68803

Is this compatible with the new raster code?

[riccardoklinger]

The proposed solution will work.
we do have the problem of translating this into .jpg . Therefore I will
used the solution form gis.stackexcchange and store a temp tif and
translate it to .jpg via
processing.runalg("gdalogr:translate",...)

will do this this week!

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On Mon, Apr 20, 2015 at 10:56 AM, Tom Chadwin notifications@github.com
wrote:

I also got an answer on StackExchange:

http://gis.stackexchange.com/questions/68803/qgis-save-raster-as-rendered-image?noredirect=1#comment207705_68803

Is this compatible with the new raster code?

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