Remove “quality†property from JPG
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up vote
3
down vote
favorite
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
metadata jpeg
asked yesterday
DarkoG
185
 |Â
show 3 more comments
up vote
3
down vote
favorite
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
metadata jpeg
asked yesterday
DarkoG
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
 |Â
show 3 more comments
up vote
3
down vote
favorite
up vote
3
down vote
favorite
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
metadata jpeg
asked yesterday
DarkoG
185
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
metadata jpeg
asked yesterday
DarkoG
185
edited yesterday
asked yesterday
DarkoG
185
asked yesterday
DarkoG
185
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
 |Â
show 3 more comments
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
 |Â
show 3 more comments
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.
answered yesterday
szulat
3,31011025
You have a typo there,s/Independend/Independent. Too small for me to suggest the edit.
– KRyan
45 mins ago
add a comment |Â
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.
answered yesterday
StarGeek
1,43158
add a comment |Â
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.
answered yesterday
xiota
3,217941
add a comment |Â
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.
answered yesterday
szulat
3,31011025
You have a typo there,s/Independend/Independent. Too small for me to suggest the edit.
– KRyan
45 mins ago
add a comment |Â
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.
answered yesterday
szulat
3,31011025
You have a typo there,s/Independend/Independent. Too small for me to suggest the edit.
– KRyan
45 mins ago
add a comment |Â
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.
answered yesterday
szulat
3,31011025
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.
answered yesterday
szulat
3,31011025
answered yesterday
szulat
3,31011025
answered yesterday
szulat
3,31011025
answered yesterday
szulat
3,31011025
3,31011025
You have a typo there,s/Independend/Independent. Too small for me to suggest the edit.
– KRyan
45 mins ago
add a comment |Â
You have a typo there,s/Independend/Independent. Too small for me to suggest the edit.
– KRyan
45 mins ago
You have a typo there,
s/Independend/Independent. Too small for me to suggest the edit.– KRyan
45 mins ago
You have a typo there,
s/Independend/Independent. Too small for me to suggest the edit.– KRyan
45 mins ago
add a comment |Â
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.
answered yesterday
StarGeek
1,43158
add a comment |Â
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.
answered yesterday
StarGeek
1,43158
add a comment |Â
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.
answered yesterday
StarGeek
1,43158
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.
answered yesterday
StarGeek
1,43158
edited yesterday
answered yesterday
StarGeek
1,43158
answered yesterday
StarGeek
1,43158
answered yesterday
StarGeek
1,43158
1,43158
add a comment |Â
add a comment |Â
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.
answered yesterday
xiota
3,217941
add a comment |Â
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.
answered yesterday
xiota
3,217941
add a comment |Â
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.
answered yesterday
xiota
3,217941
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.
answered yesterday
xiota
3,217941
answered yesterday
xiota
3,217941
answered yesterday
xiota
3,217941
answered yesterday
xiota
3,217941
3,217941
add a comment |Â
add a comment |Â
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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