I need my photo-editor app to preserve unknown metadata entries that were existing in the original photo that was opened by my app (for example, non-standard XMP meta-data)
I tried to use the Apple's built-in meta-data read/write meta-data, with no success.
Is there a way to just copy all existing meta-data to a buffer, write it as-is and then change only specific entries?
Yes.
Use Adobe XMP SDK.
Read the metadata from the image when you open it using:
SXMPFiles myFile;
ok = myFile.OpenFile(filename, kXMP_UnknownFile, opts);
myFile.GetXMP(_meta); // _meta is a data member of the class that represents your photo (probably a subclass of NSDocument).
When saving the image, write the image content, then write _meta to the output file using SXMPFiles.PutXMP(...), and then set specific metadata entries that you like.
See Adobe XMP programming guide for more details about reading and writing XMP metadata.
Related
I try to add a thumbnail to a JPEG picture using libexif.
For now I'm borrowing the code from exif (the command line tool that is shipped by the libexif team).
However I noticed the XMP tags get deleted from the metadata. There is an old bugreport here.
I tried to see how to achieve this anyway with libexif but I don't really understand how to get the XMP from input file and put it in the output file. I just want to copy all XMP data, I don't need to extract anything of it.
I saw there is a TAG EXIF_TAG_XML_PACKET in exif_tag.h but couldn't figure out how to read/write this tag.
A related solution is in this SO answer but it looks complicated. I'm not familiar coding in C.
Is it actually possible to keep all XMP when using only libexif API? Have things changed in recent years on that? How would you write this in code?
Thanks
I believe it should be somewhat straightforward. XMP fields are described in the ISO/Adobe standard. Regular Kotlin/Java/Android file I/O and some string manipulation should be all that is required.
I would start out by becoming intimately familiar with ISO 16684-1:2019. Then, write a method for your jpeg file class that grabs all the XMP fields. Store those fields in a temp file (to prevent difficult to recover data loss in the event of your code or libexif crashing). Hand the file off to libexif. Generate the thumbnail. Finally, when that's done you can restore the XMP fields. If the thumbnail is stored in an XMP field as well (and it sounds like it is), it may be easier to concatenate that field with the other ones which were already grabbed, updating the temp file so that it contains EVERY XMP field, before adding all of the XMP fields back to the jpeg.
Unfortunately, I do not currently have the time to read a 50 page ISO standard, synthesize the information, and then write the code to implement the solution. Here's a link to the standard at least, to get you started.
https://www.iso.org/obp/ui/#iso:std:iso:16684:-1:ed-2:v1:en
I'm trying to create a web service in PHP that can deliver an SVG with reference to a PNG raster image. Both the data for the SVG as well as the binary PNG image come from a MySQL database on the server.
Option A: Encode the PNG data in base-64 and embed it directly in the SVG, such as:
<image xlink:href="data:image/png;base64,..."/>
Concerns: 30% heavier load than loading it as pure binary and noticeable delay when loading it with Postman (or is this just because of Postman).
Option B: Call the PNG data as binary and save it as a file on the file system, then call the SVG file, which would then reference the physical PNG file.
Concerns: Involvement of the file system (which implies I need to start managing physical files, expiration dates etc).
Is there perhaps another way that an SVG can reference the binary data on the fly without it having to be on the file system?
To accomplish something similar (in my case sending data for SVGs with additional data about each file as binary files, which are much smaller than sending xml, text, or json) - I use CBOR. In my case, I compress the SVG using LZString compression first, and add this along with additional data attributes to a JSON object. Then I convert the JSON object to CBOR. I think CBOR can handle your base 64 data without any need for conversion - more information about it is here: cbor.io
I found a PHP library for CBOR here: https://github.com/2tvenom/CBOREncode
This may not be the way to go at all for you, but I thought I'd throw it out there just in case.
I need to play a mp3 file from gridfs in mongodb. I will get a file-like object instead filename (to the system disk).
I cannot find anyway to use SoundLoader to play the file like object directly. I checked the code here https://kivy.org/docs/_modules/kivy/core/audio.html. it seems that kivy audio does not suppot it. Am I right? I mean, like wave module, you can open it with file like object. I prefer not to use wave because it may has issues in different OSs.
wave.open(file[, mode])
If file is a string, open the file by that
name, otherwise treat it as a seekable file-like object.
Any other way to load the data to SouldLoader instead of filename? Many thanks.
This may not be a direct answer but could be an alternative for now. I can use GridFSBucket in GridFS to download the file in stream then save temp file to disk. Finally load by SoundLoader. With this way, it would solve the problem with large media file issue. This solution also works for image or video but require some disk storage of course.
how can I create file (PDF file for example) from binary stream I have stored in global? I have stream stored in caché global and I need to create and save the file created by the stream using ObjectScript.
Thanks :)
It is not so easy. There is only one official way to create pdf in Cache, and it is ZEN reports. With ZEN reports you could create not only pdf, also possible to make html, xlsx. ZEN Reports used Apache FOP for generating it, any other ways also possible, but you should do it only by yourself.
Or maybe I misunderstood you, and you mean that your binary stream already contains PDF, and you just want to save it to some file. If so, you just have to copy your globalstream to filestream, with code like this:
set fs=##class(%Stream.FileBinary).%New()
set fs.Filename="c:\temp.pdf"
set tSC=fs.CopyFrom(yourStream)
set tSC=fs.%Save()
Many photo viewing and editing applications allow you to examine and change EXIF and IPTC data in JPEG and other image files. For example, I can see things like shutter speed, aperture and orientation in the picture files that come off my Canon A430. There are many, many name/value pairs in all this metadata. But...
What do I do if I want to store some data that doesn't have a build-in field name. Let's say I'm photographing an athletics competition and I want to tag every photo with the competitor's bib number. Can I create a "bib_number" field and assign it a values of "0001", "5478", "8124" etc, and then search for all photos with bib_number="5478"?
I've spent a few hours searching and the best I can come up with is to put this custom information in the "keywords" field but this isn't quite what I'm after. With this socution I'd have to craft a query like "keywords contains bib_number_5478" whereas what I want it "bib_number is 5478".
So do the EXIF and/or IPTC standards allow addtional user-defined field names?
Thanks
Kev
It can be used for that, but it really shouldn't: it's meant to be user-editable and so isn't a safe place to put critical metadata. Using an XMP sidecar is better for this kind of thing: in XMP, any field added that a given app does not understand is, according to the standard, supposed to be ignored by that app and not destroyed.
I don't know if there are applications to do this but by the standards described for JPEG files there is a field called Comments where you can assign values that could act like tags.
C# code:
using System.Windows.Media.Imaging;
using System.IO;
...
FileStream fs = new FileStream(#"<img_path>", FileMode.Open, FileAccess.ReadWrite);
BitmapMetadata bmd = (BitmapMetadata)BitmapFrame.Create(fs).Metadata;
bmd.Comment = "Some Comment Here";
also if you are looking for an application that already has this functionality built into it, then might i recommend Irfan View (open pic, go to Image menu, click on Comments button).
Hope this helps.