Read Wrong Resolution

Started by Luca, October 23, 2017, 04:58:06 AM

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Luca

October 23, 2017, 04:58:06 AM
Hi,

I use exitfool to read image information for my site. It works fine for most images but sometimes it gives me a wrong resolution. XResolution and YResolution are set to 1.
The OP is linux and the exiftool version is 10.64
Output from command line: exiftool -G1 -s -a <file>
Code Select

[ExifTool]      ExifToolVersion                 : 10.64
[System]        FileName                        : image1.jpg
[System]        Directory                       : ../../Desktop
[System]        FileSize                        : 3.5 MB
[System]        FileModifyDate                  : 2017:10:20 11:24:24+02:00
[System]        FileAccessDate                  : 2017:10:23 09:06:21+02:00
[System]        FileInodeChangeDate             : 2017:10:20 11:24:24+02:00
[System]        FilePermissions                 : rwxrw-rw-
[File]          FileType                        : JPEG
[File]          FileTypeExtension               : jpg
[File]          MIMEType                        : image/jpeg
[File]          ExifByteOrder                   : Big-endian (Motorola, MM)
[File]          Comment                         : CREATOR: gd-jpeg v1.0 (using IJG JPEG v62), quality = 100.
[File]          ImageWidth                      : 2560
[File]          ImageHeight                     : 1600
[File]          EncodingProcess                 : Baseline DCT, Huffman coding
[File]          BitsPerSample                   : 8
[File]          ColorComponents                 : 3
[File]          YCbCrSubSampling                : YCbCr4:2:0 (2 2)
[JFIF]          JFIFVersion                     : 1.01
[JFIF]          ResolutionUnit                  : None
[JFIF]          XResolution                     : 1
[JFIF]          YResolution                     : 1
[IFD0]          XResolution                     : 1
[IFD0]          YResolution                     : 1
[IFD0]          ResolutionUnit                  : None
[IFD0]          YCbCrPositioning                : Centered
[Composite]     ImageSize                       : 2560x1600
[Composite]     Megapixels                      : 4.1
If i open the image with a program like gimp or photoshop i can retrive these information as 96dpi.
There is any way to retrive these correct information with exiftool?.

An example image can be found here: http://farnet.thepot.site/example/image1.jpg

Phil Harvey

#1
October 23, 2017, 07:22:27 AM
ExifTool is of course correct.  I don't know why the other software reports otherwise.

I opened this in Photoshop but can't find where it tells me the resolution.  The image you posted contains JFIF resolutions but not EXIF resolutions, so it is different from the metadata you posted.

- Phil
...where DIR is the name of a directory/folder containing the images.  On Mac/Linux/PowerShell, use single quotes (') instead of double quotes (") around arguments containing a dollar sign ($).

Hayo Baan

#2
October 23, 2017, 03:59:48 PM
Interesting, Photoshop, Preview, and PhotoMechanic all tell me the resolution is 72ppi.
I'm thinking they don't look at the JFIF resolution at all (or assume 1 is incorrect) and revert to a default (72ppi)
Hayo Baan – Photography
Web: www.hayobaan.nl

StarGeek

#3
October 23, 2017, 06:44:40 PM
What are the results in those programs when you add Photoshop:XResolution and Photoshop:YResolution?
"It didn't work" isn't helpful. What was the exact command used and the output.
Read FAQ #3 and use that cmd
Please use the Code button for exiftool output

Please include your OS/Exiftool version/filetype

Jaap

#4
February 01, 2018, 06:10:14 AM
I've found a similar issue with the attached file. The JFIF XResolution and YResolution report '1', while Photoshop reports 72dpi. You can check this in Photoshop via Image -> Image Size (see screenshot attached).

Output for exiftool -G1 -s -a
Code Select

[ExifTool]      ExifToolVersion                 : 10.55
[System]        FileName                        : test-incorrect-reso.jpg
[System]        FileSize                        : 1178 kB
[System]        FileModifyDate                  : 2018:02:01 11:56:09+01:00
[System]        FileAccessDate                  : 2018:02:01 11:56:11+01:00
[System]        FileInodeChangeDate             : 2018:02:01 11:56:09+01:00
[System]        FilePermissions                 : rw-r--r--
[File]          FileType                        : JPEG
[File]          FileTypeExtension               : jpg
[File]          MIMEType                        : image/jpeg
[File]          ExifByteOrder                   : Big-endian (Motorola, MM)
[File]          ImageWidth                      : 2365
[File]          ImageHeight                     : 1774
[File]          EncodingProcess                 : Progressive DCT, Huffman coding
[File]          BitsPerSample                   : 8
[File]          ColorComponents                 : 3
[File]          YCbCrSubSampling                : YCbCr4:2:0 (2 2)
[JFIF]          JFIFVersion                     : 1.01
[JFIF]          ResolutionUnit                  : None
[JFIF]          XResolution                     : 1
[JFIF]          YResolution                     : 1
[ICC-header]    ProfileCMMType                  : Lino
[ICC-header]    ProfileVersion                  : 2.1.0
[ICC-header]    ProfileClass                    : Display Device Profile
[ICC-header]    ColorSpaceData                  : RGB
[ICC-header]    ProfileConnectionSpace          : XYZ
[ICC-header]    ProfileDateTime                 : 1998:02:09 06:49:00
[ICC-header]    ProfileFileSignature            : acsp
[ICC-header]    PrimaryPlatform                 : Microsoft Corporation
[ICC-header]    CMMFlags                        : Not Embedded, Independent
[ICC-header]    DeviceManufacturer              : IEC
[ICC-header]    DeviceModel                     : sRGB
[ICC-header]    DeviceAttributes                : Reflective, Glossy, Positive, Color
[ICC-header]    RenderingIntent                 : Perceptual
[ICC-header]    ConnectionSpaceIlluminant       : 0.9642 1 0.82491
[ICC-header]    ProfileCreator                  : HP
[ICC-header]    ProfileID                       : 0
[ICC_Profile]   ProfileCopyright                : Copyright (c) 1998 Hewlett-Packard Company
[ICC_Profile]   ProfileDescription              : sRGB IEC61966-2.1
[ICC_Profile]   MediaWhitePoint                 : 0.95045 1 1.08905
[ICC_Profile]   MediaBlackPoint                 : 0 0 0
[ICC_Profile]   RedMatrixColumn                 : 0.43607 0.22249 0.01392
[ICC_Profile]   GreenMatrixColumn               : 0.38515 0.71687 0.09708
[ICC_Profile]   BlueMatrixColumn                : 0.14307 0.06061 0.7141
[ICC_Profile]   DeviceMfgDesc                   : IEC http://www.iec.ch
[ICC_Profile]   DeviceModelDesc                 : IEC 61966-2.1 Default RGB colour space - sRGB
[ICC_Profile]   ViewingCondDesc                 : Reference Viewing Condition in IEC61966-2.1
[ICC_Profile]   Luminance                       : 76.03647 80 87.12462
[ICC_Profile]   Technology                      : Cathode Ray Tube Display
[ICC_Profile]   RedTRC                          : (Binary data 2060 bytes, use -b option to extract)
[ICC_Profile]   GreenTRC                        : (Binary data 2060 bytes, use -b option to extract)
[ICC_Profile]   BlueTRC                         : (Binary data 2060 bytes, use -b option to extract)
[ICC-view]      ViewingCondIlluminant           : 19.6445 20.3718 16.8089
[ICC-view]      ViewingCondSurround             : 3.92889 4.07439 3.36179
[ICC-view]      ViewingCondIlluminantType       : D50
[ICC-meas]      MeasurementObserver             : CIE 1931
[ICC-meas]      MeasurementBacking              : 0 0 0
[ICC-meas]      MeasurementGeometry             : Unknown
[ICC-meas]      MeasurementFlare                : 0.999%
[ICC-meas]      MeasurementIlluminant           : D65
[ExifIFD]       ColorSpace                      : sRGB
[ExifIFD]       ExifImageWidth                  : 2365
[ExifIFD]       ExifImageHeight                 : 1774
[XMP-x]         XMPToolkit                      : Image::ExifTool 8.95
[XMP-xmpMM]     DocumentID                      : xmp.did:445defc3-7160-4d12-a28d-1e1a2be86649
[XMP-xmpMM]     InstanceID                      : xmp.iid:445defc3-7160-4d12-a28d-1e1a2be86649
[XMP-xmpMM]     OriginalDocumentID              : xmp.did:445defc3-7160-4d12-a28d-1e1a2be86649
[Composite]     ImageSize                       : 2365x1774
[Composite]     Megapixels                      : 4.2

Phil Harvey

#5
February 01, 2018, 07:08:16 AM
I don't think this is an ExifTool issue.  ExifTool is reporting the resolution stored in the file.  My guess is that Photoshop has set some limits on reasonable resolutions and defaults to 72 dpi if the stored resolutions are outside these limits.

- Phil
...where DIR is the name of a directory/folder containing the images.  On Mac/Linux/PowerShell, use single quotes (') instead of double quotes (") around arguments containing a dollar sign ($).

Jaap

#6
February 01, 2018, 07:47:12 AM
Thanks for your quick reply. I guess there are tools out there that write incorrect resolution info into the file metadata. Your assumption on the Photoshop behavior makes sense.

Thanks for your feedback,
Jaap

Phil Harvey

#7
February 01, 2018, 07:51:49 AM
Under the category of "learn something new every day", from the JFIF specification:

"if you only want to specify a pixel aspect ratio, put 0 for the units field in the special APP0 field. Xdensity and Ydensity can then be programmed for the desired aspect ratio. Xdensity = 1, Ydensity = 1 will program a 1:1 aspect ratio. Xdensity and Ydensity should always be non-zero."

So this is not an error.

I guess this makes some sense, because the units are set to "None":

Code Select
> exiftool ~/Desktop/test-incorrect-reso.jpg -jfif:all
JFIF Version                    : 1.01
Resolution Unit                 : None
X Resolution                    : 1
Y Resolution                    : 1

- Phil
...where DIR is the name of a directory/folder containing the images.  On Mac/Linux/PowerShell, use single quotes (') instead of double quotes (") around arguments containing a dollar sign ($).

Jaap

#8
February 01, 2018, 08:22:23 AM
Ahaaa, right... Speaking about confusing standards ;)

Anyway this makes sense now. I will probably ignore the JFIF X and Y Resolution values when the Resolution Unit is set to None (and default to 72ppi like PS is doing).

The actual data in these fields is still incorrect though as it's not a square image (Not an ExifTool problem).

Thanks again Phil :)
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