Pyramids v ArcMap a ArcGIS Pro

Y_Chau

Mám několik 16bitových dronových snímků. Všiml jsem si, že pyramidové soubory generované pro tyto snímky v ArcMap jsou 6krát menší než v ArcGIS Pro. Mohu také použít soubory OVR z ArcMap v Pro a není viditelný žádný rozdíl ve výkonu. Máte nějaký nápad, proč by mohl být tak velký rozdíl ve velikosti pyramidových souborů?

S pozdravem

PeterBecker

I tool a look. This is a strange file. It appears to be drone imagery that was originally 8bit and has been exported as a 12bit JPEG compressed image with 256 being defined as NoData and set using JPEG12bit compression . It is not clear to me if this the original image rotated or export from an orthorectification process. Such processing creates artifacts at the edges. (In the following I set NoData to organize to highlight the issue)

JPEG has an issue in that traditionally it does not have NoData. The software that produced the image (could have been ArcMap) set NoData as 256. Please check this and set to 255 instead which would keep it in the 8bit range and compress much better. You will still see the JPEG artifacts. There are different ways to handle the masking of 8bit JPEG but it depends on how the image was exported.

The 12bit version of JPEG is not natively supported in ArcGIS Pro hence it is converting to 16bit and using Deflate (lossless) compression hence the increase in size. There is a relatively complex work around using GLAD that can be done, but I recommend checking first on the source of how the images were created.