IM convert leads to loss of details on a 16-bit tif image

[snibgo]

For some operations (and output types), IM will count the number of values in the image, and save as 8-bit if that doesn't discard data. For example:

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convert 1481059547.tiff x.png

x.png is only 8-bit/channel.

Perhaps when PS proceses 8-bit files, it processes in only 8 bits.

[swiss_knight]

Hi,

I confirm the image I uploaded was the original one (no IM command used before, it's a raw image).
So, by only doing:

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convert myimage.tif output2.tif 

the result is as seen before; there is some kind of compression -> quality loss.
Plus, there is some strange stripes at the right of the image. Here are the original and output image again, print screen from Photoshop:

Original:

IM processed:

(at this zoomed out level, the quality loss is not discernible, but it is really there as show on previous page).


Here are the differences between the two files (left=original, right=output) with the

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identify -verbose

command:

No real infos here...


And here's the result from

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exiftool -all -G0

( http://www.sno.phy.queensu.ca/~phil/exiftool/ ):

(lot of EXIF data are lost after using ImageMagick.....)

I was also wondering... this may be a Photoshop issue, but in that case, why does the images processed with gdal for example look exactly like the original and not the ones processed with IM?

I also tried to visualize input and output images on a raw processing software for Photographs (Darktable) on my Linux platform, I can also see the loss of detail on the output image...


Thanks a lot for your help!

[snibgo]

Something strange is happening. For example, with IM v6.9.5-3:

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convert 1481059547.tiff a1.png

When viewed in Microsoft Photo Viewer, 1481059547.tiff looks almost black, but a1.png has clear "noise" in a strip down the right side.

I can't explain that. Perhaps a developer will take a look.