Remove “quality” property from JPG

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up vote
3
down vote

favorite
1












I noticed some photos missing "quality" information in their metadata using ImageMagick's identify command



identify -verbose image.jpg


How can one remove this info?



This is one example



enter image description here




metadata jpeg




share|improve this question

















  • 8




    A little bit more detail would be nice. What are you trying to achieve?
    – flolilolilo
    yesterday










  • I am trying to understand how this works. My ultimate goal is to strip as much as possible metadata from the image to reduce its size. For me every byte is important as long as the image quality is intact.
    – DarkoG
    yesterday







  • 1




    null, this has nothing to do with the exiftool and is separate discussion, the "quality" still exist even after exiftool.
    – DarkoG
    yesterday






  • 2




    @DarkoG Then why not strip the EXIF info altogether?
    – Michael Clark
    yesterday






  • 2




    As an aside, you probably want to look at Guetzli rather than messing about trying to save a few bytes of metadata.
    – Philip Kendall
    yesterday
















up vote
3
down vote

favorite
1












I noticed some photos missing "quality" information in their metadata using ImageMagick's identify command



identify -verbose image.jpg


How can one remove this info?



This is one example



enter image description here




metadata jpeg




share|improve this question

















  • 8




    A little bit more detail would be nice. What are you trying to achieve?
    – flolilolilo
    yesterday










  • I am trying to understand how this works. My ultimate goal is to strip as much as possible metadata from the image to reduce its size. For me every byte is important as long as the image quality is intact.
    – DarkoG
    yesterday







  • 1




    null, this has nothing to do with the exiftool and is separate discussion, the "quality" still exist even after exiftool.
    – DarkoG
    yesterday






  • 2




    @DarkoG Then why not strip the EXIF info altogether?
    – Michael Clark
    yesterday






  • 2




    As an aside, you probably want to look at Guetzli rather than messing about trying to save a few bytes of metadata.
    – Philip Kendall
    yesterday












up vote
3
down vote

favorite
1









up vote
3
down vote

favorite
1






1





I noticed some photos missing "quality" information in their metadata using ImageMagick's identify command



identify -verbose image.jpg


How can one remove this info?



This is one example



enter image description here




metadata jpeg




share|improve this question













I noticed some photos missing "quality" information in their metadata using ImageMagick's identify command



identify -verbose image.jpg


How can one remove this info?



This is one example



enter image description here





metadata jpeg





share|improve this question












share|improve this question




share|improve this question








edited yesterday
























asked yesterday









DarkoG

185




185







  • 8




    A little bit more detail would be nice. What are you trying to achieve?
    – flolilolilo
    yesterday










  • I am trying to understand how this works. My ultimate goal is to strip as much as possible metadata from the image to reduce its size. For me every byte is important as long as the image quality is intact.
    – DarkoG
    yesterday







  • 1




    null, this has nothing to do with the exiftool and is separate discussion, the "quality" still exist even after exiftool.
    – DarkoG
    yesterday






  • 2




    @DarkoG Then why not strip the EXIF info altogether?
    – Michael Clark
    yesterday






  • 2




    As an aside, you probably want to look at Guetzli rather than messing about trying to save a few bytes of metadata.
    – Philip Kendall
    yesterday












  • 8




    A little bit more detail would be nice. What are you trying to achieve?
    – flolilolilo
    yesterday










  • I am trying to understand how this works. My ultimate goal is to strip as much as possible metadata from the image to reduce its size. For me every byte is important as long as the image quality is intact.
    – DarkoG
    yesterday







  • 1




    null, this has nothing to do with the exiftool and is separate discussion, the "quality" still exist even after exiftool.
    – DarkoG
    yesterday






  • 2




    @DarkoG Then why not strip the EXIF info altogether?
    – Michael Clark
    yesterday






  • 2




    As an aside, you probably want to look at Guetzli rather than messing about trying to save a few bytes of metadata.
    – Philip Kendall
    yesterday







8




8




A little bit more detail would be nice. What are you trying to achieve?
– flolilolilo
yesterday




A little bit more detail would be nice. What are you trying to achieve?
– flolilolilo
yesterday












I am trying to understand how this works. My ultimate goal is to strip as much as possible metadata from the image to reduce its size. For me every byte is important as long as the image quality is intact.
– DarkoG
yesterday





I am trying to understand how this works. My ultimate goal is to strip as much as possible metadata from the image to reduce its size. For me every byte is important as long as the image quality is intact.
– DarkoG
yesterday





1




1




null, this has nothing to do with the exiftool and is separate discussion, the "quality" still exist even after exiftool.
– DarkoG
yesterday




null, this has nothing to do with the exiftool and is separate discussion, the "quality" still exist even after exiftool.
– DarkoG
yesterday




2




2




@DarkoG Then why not strip the EXIF info altogether?
– Michael Clark
yesterday




@DarkoG Then why not strip the EXIF info altogether?
– Michael Clark
yesterday




2




2




As an aside, you probably want to look at Guetzli rather than messing about trying to save a few bytes of metadata.
– Philip Kendall
yesterday




As an aside, you probably want to look at Guetzli rather than messing about trying to save a few bytes of metadata.
– Philip Kendall
yesterday










3 Answers
3






active

oldest

votes

















up vote
29
down vote



accepted










In short: there is no reason to care about this value and it its presence does not make your file larger.



identify -verbose filename(s)


only displays the quality if the image uses the standard quantization matrix. You can use nonstandard matrix (-define jpeg:q-table=...) to make this value disappear.



The quality will be, however still displayed when the (better) command



identify -format 'the quality of %f is %Q' filename(s)


is used (better for displaying the quality that is, it only looks for this value instead of performing the detailed analysis of the image, which makes it much faster than "identify -verbose")



The thing is, you can't really remove the quality value, similarly how you can't "remove" the image width or height. It is the inherent attribute of the JPEG image and is calculated by ImageMagick from the JPEG quantization tables contained in the file.



It does not have, however, any standarized meaning. The value displayed by ImageMagick corresponds to the Independed JPEG Group's libjpeg quality setting (also used in GIMP and many others), other software packages can have their own incompatible quality measures. In such nonstandard case, ImageMagick can only estimate the quality, by looking what standard quality table is similar to the actual one. Use the "-debug All" will (among others) display the following:



Quality: 85 (exact)


or



Quality: 85 (approximate)


For some reason, "-verbose" only displays the value when it is exact, while "-format %Q" will always display the quality, even if it is just approximate.






share|improve this answer





















  • You have a typo there, s/Independend/Independent. Too small for me to suggest the edit.
    – KRyan
    14 mins ago


















up vote
9
down vote













This isn't metadata that can be stripped. It's an analysis of the compression calculated from the quantization tables. When it's comes back unknown, the jpeg was compressed using a program that isn't known to identify.



See this SuperUser answer.



Edit: Upvotes for @szulat answer, much more detailed than mine.






share|improve this answer






























    up vote
    1
    down vote













    As stated by szulat and StarGeek, "quality" is not a property that can be removed from a JPEG image.



    If your purpose is to remove metadata, you can use any of the following commands:



    exiftool -All= image.jpg
    jpegoptim -s image.jpg


    Some image sharing sites automatically remove metadata.






    share|improve this answer





















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      3 Answers
      3






      active

      oldest

      votes








      3 Answers
      3






      active

      oldest

      votes









      active

      oldest

      votes






      active

      oldest

      votes








      up vote
      29
      down vote



      accepted










      In short: there is no reason to care about this value and it its presence does not make your file larger.



      identify -verbose filename(s)


      only displays the quality if the image uses the standard quantization matrix. You can use nonstandard matrix (-define jpeg:q-table=...) to make this value disappear.



      The quality will be, however still displayed when the (better) command



      identify -format 'the quality of %f is %Q' filename(s)


      is used (better for displaying the quality that is, it only looks for this value instead of performing the detailed analysis of the image, which makes it much faster than "identify -verbose")



      The thing is, you can't really remove the quality value, similarly how you can't "remove" the image width or height. It is the inherent attribute of the JPEG image and is calculated by ImageMagick from the JPEG quantization tables contained in the file.



      It does not have, however, any standarized meaning. The value displayed by ImageMagick corresponds to the Independed JPEG Group's libjpeg quality setting (also used in GIMP and many others), other software packages can have their own incompatible quality measures. In such nonstandard case, ImageMagick can only estimate the quality, by looking what standard quality table is similar to the actual one. Use the "-debug All" will (among others) display the following:



      Quality: 85 (exact)


      or



      Quality: 85 (approximate)


      For some reason, "-verbose" only displays the value when it is exact, while "-format %Q" will always display the quality, even if it is just approximate.






      share|improve this answer





















      • You have a typo there, s/Independend/Independent. Too small for me to suggest the edit.
        – KRyan
        14 mins ago















      up vote
      29
      down vote



      accepted










      In short: there is no reason to care about this value and it its presence does not make your file larger.



      identify -verbose filename(s)


      only displays the quality if the image uses the standard quantization matrix. You can use nonstandard matrix (-define jpeg:q-table=...) to make this value disappear.



      The quality will be, however still displayed when the (better) command



      identify -format 'the quality of %f is %Q' filename(s)


      is used (better for displaying the quality that is, it only looks for this value instead of performing the detailed analysis of the image, which makes it much faster than "identify -verbose")



      The thing is, you can't really remove the quality value, similarly how you can't "remove" the image width or height. It is the inherent attribute of the JPEG image and is calculated by ImageMagick from the JPEG quantization tables contained in the file.



      It does not have, however, any standarized meaning. The value displayed by ImageMagick corresponds to the Independed JPEG Group's libjpeg quality setting (also used in GIMP and many others), other software packages can have their own incompatible quality measures. In such nonstandard case, ImageMagick can only estimate the quality, by looking what standard quality table is similar to the actual one. Use the "-debug All" will (among others) display the following:



      Quality: 85 (exact)


      or



      Quality: 85 (approximate)


      For some reason, "-verbose" only displays the value when it is exact, while "-format %Q" will always display the quality, even if it is just approximate.






      share|improve this answer





















      • You have a typo there, s/Independend/Independent. Too small for me to suggest the edit.
        – KRyan
        14 mins ago













      up vote
      29
      down vote



      accepted







      up vote
      29
      down vote



      accepted






      In short: there is no reason to care about this value and it its presence does not make your file larger.



      identify -verbose filename(s)


      only displays the quality if the image uses the standard quantization matrix. You can use nonstandard matrix (-define jpeg:q-table=...) to make this value disappear.



      The quality will be, however still displayed when the (better) command



      identify -format 'the quality of %f is %Q' filename(s)


      is used (better for displaying the quality that is, it only looks for this value instead of performing the detailed analysis of the image, which makes it much faster than "identify -verbose")



      The thing is, you can't really remove the quality value, similarly how you can't "remove" the image width or height. It is the inherent attribute of the JPEG image and is calculated by ImageMagick from the JPEG quantization tables contained in the file.



      It does not have, however, any standarized meaning. The value displayed by ImageMagick corresponds to the Independed JPEG Group's libjpeg quality setting (also used in GIMP and many others), other software packages can have their own incompatible quality measures. In such nonstandard case, ImageMagick can only estimate the quality, by looking what standard quality table is similar to the actual one. Use the "-debug All" will (among others) display the following:



      Quality: 85 (exact)


      or



      Quality: 85 (approximate)


      For some reason, "-verbose" only displays the value when it is exact, while "-format %Q" will always display the quality, even if it is just approximate.






      share|improve this answer













      In short: there is no reason to care about this value and it its presence does not make your file larger.



      identify -verbose filename(s)


      only displays the quality if the image uses the standard quantization matrix. You can use nonstandard matrix (-define jpeg:q-table=...) to make this value disappear.



      The quality will be, however still displayed when the (better) command



      identify -format 'the quality of %f is %Q' filename(s)


      is used (better for displaying the quality that is, it only looks for this value instead of performing the detailed analysis of the image, which makes it much faster than "identify -verbose")



      The thing is, you can't really remove the quality value, similarly how you can't "remove" the image width or height. It is the inherent attribute of the JPEG image and is calculated by ImageMagick from the JPEG quantization tables contained in the file.



      It does not have, however, any standarized meaning. The value displayed by ImageMagick corresponds to the Independed JPEG Group's libjpeg quality setting (also used in GIMP and many others), other software packages can have their own incompatible quality measures. In such nonstandard case, ImageMagick can only estimate the quality, by looking what standard quality table is similar to the actual one. Use the "-debug All" will (among others) display the following:



      Quality: 85 (exact)


      or



      Quality: 85 (approximate)


      For some reason, "-verbose" only displays the value when it is exact, while "-format %Q" will always display the quality, even if it is just approximate.







      share|improve this answer













      share|improve this answer



      share|improve this answer











      answered yesterday









      szulat

      3,31011025




      3,31011025











      • You have a typo there, s/Independend/Independent. Too small for me to suggest the edit.
        – KRyan
        14 mins ago

















      • You have a typo there, s/Independend/Independent. Too small for me to suggest the edit.
        – KRyan
        14 mins ago
















      You have a typo there, s/Independend/Independent. Too small for me to suggest the edit.
      – KRyan
      14 mins ago





      You have a typo there, s/Independend/Independent. Too small for me to suggest the edit.
      – KRyan
      14 mins ago













      up vote
      9
      down vote













      This isn't metadata that can be stripped. It's an analysis of the compression calculated from the quantization tables. When it's comes back unknown, the jpeg was compressed using a program that isn't known to identify.



      See this SuperUser answer.



      Edit: Upvotes for @szulat answer, much more detailed than mine.






      share|improve this answer



























        up vote
        9
        down vote













        This isn't metadata that can be stripped. It's an analysis of the compression calculated from the quantization tables. When it's comes back unknown, the jpeg was compressed using a program that isn't known to identify.



        See this SuperUser answer.



        Edit: Upvotes for @szulat answer, much more detailed than mine.






        share|improve this answer

























          up vote
          9
          down vote










          up vote
          9
          down vote









          This isn't metadata that can be stripped. It's an analysis of the compression calculated from the quantization tables. When it's comes back unknown, the jpeg was compressed using a program that isn't known to identify.



          See this SuperUser answer.



          Edit: Upvotes for @szulat answer, much more detailed than mine.






          share|improve this answer















          This isn't metadata that can be stripped. It's an analysis of the compression calculated from the quantization tables. When it's comes back unknown, the jpeg was compressed using a program that isn't known to identify.



          See this SuperUser answer.



          Edit: Upvotes for @szulat answer, much more detailed than mine.







          share|improve this answer















          share|improve this answer



          share|improve this answer








          edited yesterday


























          answered yesterday









          StarGeek

          1,43158




          1,43158




















              up vote
              1
              down vote













              As stated by szulat and StarGeek, "quality" is not a property that can be removed from a JPEG image.



              If your purpose is to remove metadata, you can use any of the following commands:



              exiftool -All= image.jpg
              jpegoptim -s image.jpg


              Some image sharing sites automatically remove metadata.






              share|improve this answer

























                up vote
                1
                down vote













                As stated by szulat and StarGeek, "quality" is not a property that can be removed from a JPEG image.



                If your purpose is to remove metadata, you can use any of the following commands:



                exiftool -All= image.jpg
                jpegoptim -s image.jpg


                Some image sharing sites automatically remove metadata.






                share|improve this answer























                  up vote
                  1
                  down vote










                  up vote
                  1
                  down vote









                  As stated by szulat and StarGeek, "quality" is not a property that can be removed from a JPEG image.



                  If your purpose is to remove metadata, you can use any of the following commands:



                  exiftool -All= image.jpg
                  jpegoptim -s image.jpg


                  Some image sharing sites automatically remove metadata.






                  share|improve this answer













                  As stated by szulat and StarGeek, "quality" is not a property that can be removed from a JPEG image.



                  If your purpose is to remove metadata, you can use any of the following commands:



                  exiftool -All= image.jpg
                  jpegoptim -s image.jpg


                  Some image sharing sites automatically remove metadata.







                  share|improve this answer













                  share|improve this answer



                  share|improve this answer











                  answered yesterday









                  xiota

                  3,217941




                  3,217941






















                       

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