I've been scanning some old family photos and posting them to Facebook. On the back is some information like the date or who is in the photo. So I'm dutifully entering that info into Facebook as well. But now the metadata is in Facebook, not connected to the picture itself.
If I copy/paste my scanned images subfolder, there's no metadata about who or when these pictures are from.
Is there a way to embed that info into a jpg or png?
There are ways to do this in both PNG and JPEG. The simplest way in JPEG is to inset a COMment marker with your text into the stream. You could do that with a simple C program without having to recompress the data. Just insert the comment marker after the SOF and APPn marker---it could even be write before the EOI (end of image) marker).
Some JPEG file formats (e.g. EXIF) have various predefined tags but that is format specific.
For that you'd need some image viewing application that would allow you to set the tag values.
Related
First, thanks for any and all help regarding this topic.
Sites like Facebook and Twitter strip EXIF information from images as they are uploading. My goal is to allow users to upload images to our platform (working with Nextcloud and others) with full EXIF information, however, we need to display images that do not contain EXIF information or any metadata. Without stripping and creating a second, Exif-Free image for each, is it possible to simply hide that EXIF info so that, if a user downloads that image, the EXIF is not embedded?
We were told that the only way to do this is to have a second, exif-free copy (the order of when that's created is irrelevant pre/during/post upload). I'm hoping there's a way that we can simply display such a copy without doubling our physical space requirements.
Thanks again for your help.
Exif is metadata, along with IPTC, XMP, AFCP, ICC, FPXR, MPF, JPS and a comment, just for the JFIF/JPEG file format alone. Other picture file formats support even more/other metadata.
You wrote it yourself: a download - so it's a file in any case. Pictures are files, just like executables, movies, texts, music and archives are files, too. And metadata is part of its content, so whoever accesses the raw bytes of the file can grab everything in it. Which is not "please don't look" proof. If you
create that on the fly by stripping metadata everytime a download is requested,
or if you do it once to preserve performance and instead occupy space remains your decision.
If there would be something as simple as a "don't show" feature then it would still be in the file and could be extracted easily by software written to ignore that instruction. Seriously, there's no shortcut to that - do it properly and don't spare yourself from getting work done at the wrong end.
How is fireworks able to store this extra information in a format that is otherwise flat raster. And is there any open source way to write similar vector, layered, paginated files in Png format that would be readable by fireworks?
The PNG format allows for ancillary data chunks to store metadata aside from the image itself. I don't believe anyone's actually worked out the format that Adobe stores that data in though.
Trying to pull user images via the Facebook Social Graph.
Finding it odd that no matter what I upload the image as (gif, bmp, tiff, or jpg), my call to https://graph.facebook.com/507988137/picture?type=large (my pic) always returns a jpg.
Does anyone know if I'm OK assuming that his image is always a "jpg"? I'm using php get_file_contents to pull the images & would prefer not having to sniff test them for various formats.
Facebook doesn't save the original image that you upload. Instead it converts all uploaded images to jpgs of 4 different sizes to support all the different places where the image may be displayed.
In case you are interested, Facebook basically has this down to a science, in fact, I've read several times that they are the largest image hosting service in the world. More details within this Facebook blog post, Facebook Photos Infrastructure
That's because FaceBook stores it as a jpg, because that is in general the most efficient image format for pictures.
It's always a good idea to check if the data is what you expect. Checking image type is quite easy. It will always be a web format, which basically comes down to jpg, png and gif, with gif being very unlikely because of its limitations (GIF can contain 256 colors at most, and is generally larger than png. Has license limitations too).
BMP is not a web format and cannot be displayed in most browsers. You will not get a BMP from that url.
make sure you also handle the case where a gif is returned to you.
This is the default profile pic for users that doesn't update their profile pic
I have to link a date and a name to some jpegs that I am including in my bundle, or possibly downloading from my own server to the Documents folder. Is there a way to extract EXIF data easily?
If so, then I will use EXIF to store this info. If not, then I will have to create a database or flat file that maps my extra data to the image file.
Keep in mind, these are not photos the iPhone has taken and is providing via UIImagePicker or from outside the sandbox. These are photos that I am including with the app or downloadig to the Docs folder myself. The important point here is ease:
Is it easier to
read EXIF file from my image files
have another file that keeps track of
the image file and the associated
data (could be sqlite)
Thanks!
You can try using iphone-exif toolkit to extract the data. However, it's licensed GPL and if your app is commercial you'll need to negotiate a license deal. If that's not viable then you may want to go the external meta-data route.
The actual EXIF data is stored in the form of a small TIFF file with EXIF-specific TIFF tags for information that doesn't have a home in the TIFF specification. When placed in a JPEG file (really a JFIF bitstream), it is stored in a JPEG APP1 marker which limits the total size of the EXIF data to just a bit less than 64KB.
It shouldn't be that difficult to locate the APP1 marker, confirm it contains EXIF data, and then parse out a specific collection of EXIF tags with fairly brute force coding.
One example you can look at is exiftool which does just that, and is written in Perl and open source under the same terms as Perl itself.
If these files are purely for use in your own application and will not be reused in other tools by the user, then there is some mileage in storing your data as XML/JSON in the comment segment 0xFFFE. As mentioned before you get just short of 64k to play with.
The beauty of using the comment segment is that it should be preserved by image editing tools, is quick to access (because you do not need to traverse the IFD blocks that store EXIF data, you just read/write a text string with 4 byte type/length header) and is human readable/writable in a graphics app.
I would avoid storing the associated data in a db if practical, so that you don't risk the db becoming out of sync with the available files.
I use ExifTool
embedded in my app. Works a treat.
I would like to add some custom data to an image the user generates in my app, no more than 1kb tops. I could probably hide the data in the image, but I want to do this in a way that will resist resizing but not deliberate deletion of EXIF tags (say, for privacy reasons).
Is this possible using the current public SDK 3.0?
this might be helpful, though i've never used it before - iphone-exif
This could be very useful: PhotoshopFramework is one powerful library to manipulate images on Objective-C. This was developed to bring the same functionalities that Adobe Photoshop users are familiar. Examples: Set colors using RGB 0-255, apply blend filers, transformations...
Is open source, here is the project link: https://sourceforge.net/projects/photoshopframew/