Tag Archives: images

A screen capture tip using Grab on the Mac

MacOS provides a few different ways to do screen captures. My personal favorite is Grab, which is found in the Applications/Utilities folder. It lets me capture a selection, a window, or the whole screen without having to remember any magic key combinations. I keep it in the Dock for quick access.

Grab has one deficiency, though. It can save screenshots only as TIFF files. If Apple had to pick just one format, that’s hardly the most useful one. But there’s an easy workaround.

After you’ve got your screen shot, press Command-C or choose “Copy” from the Edit menu. Open the Preview application. Press Command-N or select “New from clipboard” from the File menu. You now have the screenshot in Preview.

In Preview, press Command-S or choose “Save…” from the File menu. You’ll get a dialog to save the file, with a choice of formats: JPEG, JPEG2000, OpenEXR, PDF, PNG, or TIFF. Pick whichever one you like. If you’re going to put the image into a Web page, PNG is usually the best choice. Preview will remember your choice for next time. Then save the file.

If you prefer, you can do the equivalent in Photoshop, Gimp, or any other image-processing application, but Preview has the advantage of launching quickly and keeping the process simple.

That’s it. You can now use Grab to save screenshots to a Web-friendly format.

FUIF: Yet another image format?

A tweet led me to a pair of articles about a new file format called FUIF. That stands for “Free Universal Image Format.” Jon Sneyers describes it in a series of articles which so far include a Part 1 and Part 2.

It’s “responsive by design”; a single image file can be truncated at various offsets to produce different resolutions. Sneyers says FUIF meets JPEG’s criteria for a new format that provides “efficient coding of images with text and graphics” and “very low file size image coding.”
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How Twitter renders GIF

I’ve long wondered how Twitter renders animated GIF files. I have Firefox set to disable GIF animation, and it works everywhere except on Twitter. Apart from that, the interface indicates something is going on beyond normal GIF display. It doesn’t animate till you hit the “Play” button, and then there’s apparently no way to stop it.
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Apple’s HEIF and HEVC

At this year’s WWDC, Apple introduced a new format for still images and video. The container is called High Efficiency Image Format (HEIF), and it uses a codec called High Efficiency Video Coding (HEVC). HEIF files can store still images, video, or both at once. Apple doesn’t have proper documentation on its site, as far as I can see, but a slideshow on HEIF and one on HEVC provide a lot of information. Kelly Thompson provides a technical overview.

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PNG pulls ahead of JPEG

Every month. W3Techs records the percentage of websites using popular image file formats. For a long time, PNG was slowly creeping up on JPEG. In the latest numbers, PNG has pulled ahead, being used on 74.1% of websites, against JPEG’s 73.8%. GIF stands at a distant third with 36%, followed by SVG at 3.8%.

Keep in mind, this isn’t the same as saying more PNG images are on the Web than JPEG images. If pages which hold JPEGs contain more of them, there may be more JPEG images even if they aren’t on more sites. Since galleries of JPEG photographs are common, this is a plausible situation.

You can see the trend by looking at the RSS feed. Unfortunately, all links point to the same URL, but if you can view the RSS preview, you can get the old numbers on a monthly basis. The web page is updated daily, which is why the numbers quoted above don’t match the June numbers in the RSS feed.
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Sloppy reporting of image file hazards

Reporting carries responsibility. When you tell the public about a risk, you need to tell them what the risk is, not just scare them. An article from Check Point Software Technologies, titled “ImageGate,” shows how bad even tech sites can get at clickbait reporting. According to Wikipedia, Check Point is a business with thousands of employees, not a hole-in-the-wall IT company that hires ghostwriters to write filler.

The article claims:

the attackers have built a new capability to embed malicious code into an image file and successfully upload it to the social media website. The attackers exploit a misconfiguration on the social media infrastructure to deliberately force their victims to download the image file. This results in infection of the users’ device as soon as the end-user clicks on the downloaded file.

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Olympic file format capriciousness

This blog doesn’t generally deal with cronyist bullying operations like the International Olympic Committee (IOC). But when the IOC get silly about the file formats it tells people they can’t use, that’s a subject worth mentioning here.

The IOC has decreed that “the use of Olympic Material transformed into graphic animated formats such as animated GIFs (i.e. GIFV), GFY, WebM, or short video formats such as Vines and others, is expressly prohibited.”
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The persistence of old formats

Technologies develop to a point where they’re good enough for widespread use. Once a lot of people have adopted them, it’s hard to move on from there to a still better one, since people have invested so much in a technology that works for them. We see this with cell phone communication, which is pretty good but would undoubtedly be much better if it could be invented all over today. We see it with the DVD format, which Blu-Ray hasn’t managed to push aside in spite of huge marketing efforts. And we see it in file formats.

Most of today’s highly popular formats have been around since the nineties. For images, we still have TIFF, JPEG, PNG, and even the primitive GIF format, which goes back to the eighties. In audio, MP3 still dominates, even though there are now much better alternatives.

This is a good thing in many ways. If new, improved formats displaced old ones every five years, we’d be constantly investing in new software, and anyone who didn’t upgrade would be unable to read a lot of new files. Digital preservation would be a big headache, as archivists would need to migrate files repeatedly to avoid obsolescence.

It does mean, though, that we’re working with formats that have deficiencies which often have grown in importance. JPEG compression isn’t nearly as good as what modern techniques can manage. MP3 is encumbered with patents and offers sound quality that’s inferior to other lossy audio formats. HTML has improved through major revisions, but it’s still a mess to validate. For that matter, we have formats like “English,” which lacks any spec and is a pile of kludges that have accumulated over centuries. Try finding support for supposed improvements such as Esperanto anywhere.

It’s a situation we just have to live with. The good enough hangs on, and the better has a hard time getting acceptance. Considering how unstable the world of data would be if this weren’t the case, it’s a good thing on the whole.

Photoshop’s PSD file format

Photoshop’s native format, PSD, doesn’t get a lot of discussion. It’s Photoshop’s default format, and people use it for projects if only for that reason, so we really should know something about it. A lively place to start is “Fun Photoshop File Format Facts” on the Postlight blog. For serious investigation, look at Adobe’s specification. There’s also a short article on archiveteam.org, with some information about the format’s history.
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MRF for large images

NASA is using a format for online files, called MRF (Meta Raster Format), which is claimed to deliver images ten times as fast as JPEG2000 from cloud services when used with a compression algorithm called LERC. LERC is under patent by Esri, which says the technique is especially suited for geospatial applications and makes the algorithm “freely available to the geospatial and earth sciences community.” An implementation of MRF from NASA is available on GitHub under the Apache license, and an implementation of LERC is on GitHub from Esri.
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