Imported Orthomosaic - appears black? colors? alpha channel?

[LWR]

Hi forum!

I have a question that is probably easy to solve, but I just can't figure it out right now. (So before I try it for a long time, I just ask you briefly) - Thanks in advance!

I imported a few orthomosaics (public data), but one type has the problem that the colors disappear in Metashape.
The orthomosaic becomes black.
How can I fix this?
(I have attached two screenshots of the corresponding pictures)

Thanks in advance!
LWR

[Paulo]

Hi LWR,

it seems you are trying to import a color map as an orthomosaic. How did you export this from your GIS software.? For example if I want to export a color OpenStreet Map from Global Mapper, I will choose 24 bit RGB option File format to be able to get a color ortho in MS. If I choose Black and White file format (1 bit) I will get a black and white ortho. I I choose 8 bit then I will get a grey scale map...

see attachement where I exported a color Open Street Map as 1 bit Black/White file type and when I import into MS then it appears almost all black. To get a color orthomap in MS, I should export as 24 bit RGB

Maybe this is the issue?

[LWR]

Hi Paulo!
Thanks for the fast reply!
Unfortunately, I didn't create the file myself. This comes from an external institution over which I have no influence.
The image is georeferenced and has a bit depth of 8. Compression is "PackBits". Filetyp: "tif", with tfw-file.
The picture appears normal in other programs. Only in Agisoft it is not displayed correctly. (E.g. image editing programs such as GIMP)

[Paulo]

LWR,

can you open the Raster calculator in MS and check if ouput band 1 has a distribution of values in 0 to 255 range as in attached screen where I imported a 8 bit map into MS and checked the distribution of output band 1 in  histogram...in Transform Tab, I set output band to B1 and in Palette tab, I can see the histogram with range of values for B1 from 100 to  252 so it is a true 8 bit ortho and not 1 bit (0 or 1) B/W

[LWR]

Here the histogram looks like this:
(or in other words - there is nothing)

[LWR]

Maybe it is good to make the file available:
https://www.dropbox.com/sh/9xngchjyjx3wswk/AAD0jHuoiyzcfkx7XtJbiG86a?dl=0

[Alexey Pasumansky]

Hello LWR,

It seems that the colors in the orthomosaic occupies only 0-25 value range instead of 0-255 for 8bit colors. So for visual purposes you can use Set Brightness to 1000%.

Alternatively set Raster Transform formula to B1/25, set Palette to Grayscale (with the default 0 - 1 range).

[Paulo]

Hi LWR,

this was the trick to visualize map in grey scale. If you want to see your map with correct color palette, do following:

1. In Raster Calculator Transform Tab, set output band to B1 and Enable transform
2. In Palette Tab, set range from 0 to 31. And with Import Palette button, import file map.clr (attached).

Your map will now appear in color.

[LWR]

Thank you very much for your input!
After the hints and ideas I loaded the GeoTiff into QGIS and created the clr-map. After that, transforming into MS works very well.
Thank you for the input! (I would probably never have figured it out)