dng preview does not working

[monokini3d]

subj

[ariselseng]

@monokini3d a bit more info would be helpful. Usually when I get these issues here, it's just that the image does not have an embedded preview. Can you confirm that or upload a sample somewhere so I can have a look?

[monokini3d]

I uploaded dng files from vuescan program.

ExifTool Version Number         : 9.59
File Name                       : scan0001.dng
Directory                       : .
File Size                       : 103 MB
File Modification Date/Time     : 2023:07:18 19:40:18+05:00
File Access Date/Time           : 2023:07:19 01:42:41+05:00
File Creation Date/Time         : 2023:07:19 01:42:29+05:00
File Permissions                : rw-rw-rw-
File Type                       : DNG
MIME Type                       : image/x-adobe-dng
Exif Byte Order                 : Little-endian (Intel, II)
Make                            : Plustek
Camera Model Name               : OpticFilm 135i
Orientation                     : Horizontal (normal)
Page Name                       : Transparency
Software                        : VueScan 9 x64 (9.8.11)
Subfile Type                    : Full-resolution Image
Image Width                     : 3516
Image Height                    : 5100
Bits Per Sample                 : 16 16 16
Compression                     : Uncompressed
Photometric Interpretation      : Linear Raw
Fill Order                      : Normal
Strip Offsets                   : (Binary data 45726 bytes, use -b option to extract)
Samples Per Pixel               : 3
Rows Per Strip                  : 1
Strip Byte Counts               : (Binary data 30599 bytes, use -b option to extract)
Min Sample Value                : 0 0 0
Max Sample Value                : 65535 65535 65535
X Resolution                    : 300
Y Resolution                    : 300
Planar Configuration            : Chunky
Resolution Unit                 : inches
Create Date                     : 2023:07:18 19:40:18
DNG Version                     : 1.1.0.0
Unique Camera Model             : Plustek OpticFilm 135i
Color Matrix 1                  : 3.240625381 -1.537207961 -0.4986285865 -0.9689307213 1.875756025 0.04151752219 0.05571012199 -0.2040210515 1.056995988
As Shot White XY                : 0.3127000034 0.3289999962
Baseline Noise                  : 64
Image Size                      : 3516x5100

[monokini3d]

https://cloud.ideafix.co/index.php/s/RRGxwzBm9acrxoj - example dng file

small embedded preview is in file, i think. Windows explorer can make a thumbnail

[ariselseng]

There is no embedded preview in this file:

exiftool -json -preview:all
[{
  "SourceFile": "scan0016.dng"
}]

[monokini3d]

May be it will be good to change "error" message? Now I see something like "Error while loading filename.dng" (i see this message in my language, not in english). May be it will be more right to show something like "no preview available for filename.dng"

[ariselseng]

I am quite restricted in how the preview api in nextcloud works. To make nextcloud not try to find previews for files without a preview would make the app to the extraction twice, which is very slow for external storage.

[monokini3d]

may be, it is possible to make a fake preview via gd... a picture with a text "no preview available"

[monokini3d]

In any case, thanks for the prompt and clear answer.

[ariselseng]

may be, it is possible to make a fake preview via gd... a picture with a text "no preview available"

That could work. Thanks for the tip. I will keep that in mind.