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tvdb
Inspiring
March 25, 2020
Resuelto

Is there a way to create JPEG files without the photoshop file signature?

  • March 25, 2020
  • 1 respuesta
  • 3536 visualizaciones

When I try to upload images to some system I'm using, it fails on some JPEGs and others not. After some searching I found that at the bits and bytes level there is a signature that tells if a file is a JPEG or something else. Apparently JPEGs exported from photoshop have a slightly different signature, and apparently my system fails on them. They are still somewhat JPEGs but more like photoshop JPEGS. If I open and export the file in Gimp for example, it works without a problem.

So my question comes to if there is a way to export those images in photoshop as plain JPEG images?

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Mejor respuesta de tvdb

Sorry, should start FFE8FF.

After this there are a sequence of fields that may appear in any order. Many JPEG files start with "JFIF APP0 marker" which means they will start FFE8FFF0 (FFF0 means App0). But Photoshop uses APP14 (FFFB) in your file. Both are legal, but it may be that the person who made your system looked at a small sample of files rather than the spec. Here is a partial list of APP tags (App14 is an Adobe tag, invented in the very early days even before JFIF). Changing APP14 to APP0 will produce a header that is ignored. Photoshop data will be lost (like resolution). This may not matter.


For future reference, I solved my problem by using imageoptim. This tool has set the JFIF marker to APP0.

1 respuesta

T
Test Screen Name
Legend
March 25, 2020

No options because both are right. The real signature is only the first 4 bytes. Make sure you aren’t using CMYK, though, this isn’t widely supported in JPEG. 

    T
    tvdbAutor
    Inspiring
    March 25, 2020

    Thanks for your reply. The files are all in RGB so that's not the issue. 

     

    I checked the hex dumps and they give me the results at the bottom. I also tried to manually change the erroneous files at the bytelevel, but to no avail.

     

    The one that works starts with: FF D8 FF E0 00 10 4A 46 49 46

    The one that doesn't work: FF D8 FF ED 00 2C 50 68

    Both files end with: FF D9


    T
    Test Screen Name
    Legend
    March 25, 2020

    Bear in mind that Adobe were one of the very first adopters of JPEG, and Photoshop one of the very first apps to make JPEG files. So your real question is, what is wrong with the system you are using?

     

    All JPEG files should start FFD8FFE0. The JPEG file format is properly called JFIF, and is described in detail here: https://www.ecma-international.org/publications/files/ECMA-TR/ECMA%20TR-098.pdf This builds on the JPEG compression format, which is not described in that document. 


    Sorry, should start FFE8FF.

    After this there are a sequence of fields that may appear in any order. Many JPEG files start with "JFIF APP0 marker" which means they will start FFE8FFF0 (FFF0 means App0). But Photoshop uses APP14 (FFFB) in your file. Both are legal, but it may be that the person who made your system looked at a small sample of files rather than the spec. Here is a partial list of APP tags (App14 is an Adobe tag, invented in the very early days even before JFIF). Changing APP14 to APP0 will produce a header that is ignored. Photoshop data will be lost (like resolution). This may not matter.

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