Thursday, February 24, 2022

Canvas LMS Images Not Appearing in Safari Web Browser


Students and instructors using the Canvas Learning Management System encounter "missing graphics" placeholders when visiting the Canvas site on Apple's Safari web browser:

(Possible) Solution

Disable "Prevent cross-site tracking" feature in Safari preferences
(Caveat: This may expose the user to mechanisms which allow anonymous entities to track their activities across the World-Wide Web.)

More Information

Advertising content in web pages is typically hosted by different providers than the entity hosting the page's content. While this infrastructure is presumably used to target advertising to a given user, it also provides the potential for entities to correlate, profile and track that user's browsing activities across the internet.

In the interest of user privacy, most modern web browsers provide an option to "prevent cross-site tracking." The intention of this feature is to limit how one's browsing activities can be correlated.

However, users of some browsers - especially Apple's Safari for Mac OS - have encountered problems with accessing some legitimate site content. In particular, some users of the Canvas Learning Management System (LMS) for education find the majority of the image content of their educational course materials unavailable - the browser displays a "broken link" placeholder (see first image above). Apparently, the Canvas LMS hosts image content in a manner which resembles the 3rd-party advertising servers which are used for cross-site tracking.

Un-checking the "Prevent cross-site tracking" feature of the web browser MAY rectify image-loading in Canvas LMS.

NOTE: Disabling cross-site tracking potentially exposes the user to cross-site tracking practices. That said, many internet users do NOT have this feature available or enabled. If you are concerned about cross-site tracking, you can:
  • Turn ON "prevent cross-site tracking" features when not using Canvas LMS
  • Use a different web browser with Canvas LMS (i.e., Chrome, Firefox, Safari for iOS/iPhone)

NOTE: Disabling cross-site tracking may NOT resolve the issue in the newest versions of Safari: In this case, you should use another web browser with the site causing the issues.

Response from Canvas LMS Representative About This Issue

On May 4, 2020, a support representative of the Canvas LMS developer Instructure posted the following on this Canvas LMS community forum thread:

In early April, Apple released Safari updates that included a major update to a feature called Intelligent Tracking Protection (ITP). This feature implements new limitations to resources like files that are loaded on pages from a third-party site, and it behaves differently than similar systems implemented in other browsers like Chrome and Firefox.

This update affected the mechanism that Canvas uses to securely host and transmit uploaded files, including images. Users may experience files that fail to download, or images that fail to display. This behavior is due to redirection in the authentication implementation of Canvas’ secure file system, which Safari detects as a “third-party” site because it resides on a different domain.

Our engineering teams are actively investigating solutions to this issue, but a timeline is not yet available.

In the meantime, there are two workarounds:

For users who have access to another browser like Chrome, Firefox, or Edge, those browsers do not experience this issue. Using one of these alternative browsers is the recommended solution.
For users who only have access to Safari, temporarily disabling the “Prevent cross-site tracking” option in the browser privacy settings will restore Canvas functionality. Users may wish to only disable this option temporarily while using Canvas, and then re-enable it before using other sites. More information on this setting is available here:

Sunday, January 16, 2022

How to Export Email (or any Printable Document) as a PDF File on an iPhone or iPad

If you would like to export an email or any document from an app on your iOS (iPhone/iPad/iPod touch) device as a PDF file, you can do it using functionality built-in to the device, but the procedure is not obvious.

Here's how to do it:

Wednesday, December 15, 2021

Facebook Spoofing/Cloning - Not As Scary As It Seems

 This scam continues to be perpetrated against users of the Facebook community (currently December 2021) - this article attempts to inform users of the nature of the exploit and how they can guard against the intrusion.

UsefulBulk: Facebook Spoofing/Cloning - Not As Scary As It Seems

Saturday, October 24, 2020

Is Colorization Part of Digitally Remastering a Film?

A friend recently asked:

When they say they are digitally re-mastered, does that include the colorization technique [I had previously commented] about?

I responded: 

The ability to manipulate and even infer missing information (replacing missing frames of film, correcting physical damage mold, fading of dyes and the image-recording structures themselves) in the digital realm of computers makes makes them invaluable for working with all recorded media forms: still images, sound and moving-pictures. In these very mature disciplines, original content is converted into the digital language of computers. This is often referred to as "digitization," and includes such things as transferring the sound from a 140 year-old Edison Phonograph cylinder to scanning your children's baby photos from the original negative, to all the motion pictures in history. When you watch a movie on television (and back when we used to go to movie theaters, almost all of which have converted to digital projection), the original film was digitized to be transported and exhibited using digital devices. 

So "digitally re-mastered" is a bit of marketing hype, since no one would consider the alternatives to working with old films in the old analog realm if they could avoid it. Before there was digital manipulation of media, each stage of manipulating the content likely imposed "generational loss" on the facsimile. If you make a copy of a copy of a copy of a photograph, or an audio tape recording, or of a motion picture film in the analog realm the way all things were done before the last 40 years, the integrity of the original content suffered - it didn't look or sound as good as the original. Every movie you ever saw until the 1990s was degraded by at least three or four generations of the film production process by the time you saw it in the theater. "Signal" - the part you want - is increasingly displaced by "noise" in the process. In the digital workflow, you only have to manage noise during that first step from the real world of light and sound to the digital realm. After that, there can theoretically be zero loss of the original - 100% integrity (in practice there is quite a bit of loss incurred to economically transport the content to the user with a deliberately-designed, minimal amount of noticeable degradation).

Ideally, "re-mastering" a movie would mean getting access to the original negative film that went through the camera, and has been in storage in a secure, climate-controlled vault for decades. As mentioned previously, this one-of-a-kind recording media contains quite a bit more information that ever got to the Big Screens on the hundreds or thousands of mass-produced "release prints" that were shipped to theaters, after being copied from yet another generation-old "Intermediate Prints" used to protect the precious Camera-Original Negative (which is worth however much it cost to make the movie - so potentially hundreds of millions of dollars) - dozens of these intermediate prints were distributed to mass-duplication labs to be copied to Release Prints. 

(Today's theaters can receive movies over broadband data connections, rather than having heavy cans of film shipped around the world. Furthermore, these "prints" can not be scratched and broken over time. Remember what it was like to see a movie that had been at the Janus Theatres for two months? They looked like someone had dragged them across a gravel parking lot.)

In addition to the camera-original neg and visual effects negatives, an ideal re-mastering effort might attempt to access original sound production elements. These would included dialog recorded on the set (independently of picture), music scoring sessions, and sound effects. While these would have been meticulously edited and mixed on potentially hundreds of channels of audio, they would have been performed on equipment from the last 90 years, and older equipment would have imposed more noise on the results. So rather than use the pre-edited, pre-mixed soundtrack, a re-mastering team might consider (if available) re-mixing from dozens or hundreds of already-edited tracks of sound-striped 35mm film, or they might simply use that as a reference, and if the source materials were comprehensively archived, replicate or even improve on the original work by starting from scratch while using the completed materials as a reference. In the case of sound, one might create a stereo or surround-sound version of a film which was originally released as monophonic (although many enterprises create stereo versions of mono soundtracks with nothing but the final media - I once interviewed with a company whose primary business was stereo conversion). 

Using ever-evolving computational algorithms, the tools with which moving images can be altered continue to be improved and invented. And with them, so does the ethical question of where one crosses the line from "remaster" to "remake." If someone cleaning a world famous painting decides to paint a repair over a chipped, missing section of the painting, is that OK? If a recording of a famous singer's performance is missing, is it OK to replace that section with a piece synthesized with a sample of their voice? Or by using another singer?

In re-mastering, it is possible not only to "restore" the visual intent of the original filmmakers - their expectation of what would be exhibited in theaters, generational loss and all - but to deliver far more of that camera original information to the viewer. 

It's also possible to deliver MORE than was originally recorded, expected or intended. From any given film source material, a modern project could: 

  • Deliver higher resolution than the original camera recording by predictively synthesizing additional image information never recorded, but inferred by surrounding recorded information
  • Be presented at a higher frame rate than the original (early silent films were hand-cranked at 12 to 18 frames per second, and play back with motion too fast in modern 24 fps systems) by synthesizing digitally interpolated intermediate frames
  • Have color information never recorded
  • Be stereoscopic (3D), having never been shot with two separate lenses (most of today's "3D" movie releases are no longer shot with complicated and bulky stereo camera rigs, but are created independently by production businesses which uses software tools and tedious labor to create adequately believable stereoscopic images)

As you might imagine, these choices are polarizing amongst film historians, nerds and fans. Back in 2006, I attended a CBS Paramount Domestic Television presentation of the first completed "digitally remastered" episode of the original 1966 Star Trek series. They were planning to remaster all 79 episodes, and their product is uniquely valuable, having effectively never been off the air - perpetually in syndication. The really exciting prospect that I had been speculating to a Trekkie friend about for decades was that we'd see this show in High Definition (that was the year we bought our first HDTV), with far more image information that was ever intended. I predicted being able to see nails and taped seams in the set walls. Those shows were shot in the same 35mm film as theatrical motion pictures, even though they were only going to be viewed on the crude television system which we all used until the last decade. 

I don't remember if we knew that this was part of the project until that night, but the shocking part of the Star Trek "remastering" project was not that they had re-scanned all of the 35mm film to make beautiful high-definition masters, but they had replaced nearly every visual effects shot with a modern, digital replacement. Did they look better? Yes, perhaps. Were die-hard Trekkies/Trekkors/Trekkers going to be upset? Yeah, a lot of them were. But Paramount/CBS was looking to inject some new life into the property, and propel it into their licensing future. So they did it anyway. 

You may be aware of revisionist alterations of movies that have been "remastered" - the single most famous revision is "Han Shot First" (ask a Star Wars nerd if you don't know what this is about). 

With the power of modern tools comes the responsibility of utilizing them. We have to make good choices and respect the work of artists and craftspeople who invented and created the works we are tasked to curate and protect.

Saturday, May 18, 2019

A Flexible and Inexpensive AC Appliance Timer

As a workaround to persistent problems with our ancient X10 wireless remote system (which we've used for 26 years to control lights in our home, especially those with ridiculous original switch locations), I went searching for something like a "repeating appliance timer." 
   Timer Outlet, Nearpow Multifunctional Infinite Cycle Programmable Plug-in Digital Timer Switch with 3-Prong Outlet for Appliances, Energy-Saving Timer, 15A/1800W
This timer can control a 15 amp load, and cycle AC current with the following strategies:

  1. Daily Timing - up to 3 periods, defined by OFF and ON times of day (like a typical "appliance timer)
  2. Countdown and Turn Off - the timer will turn the AC outlet OFF after up after a delay from 1 minute to (I think) 23 hours, and 59 minutes; It can optionally sound a built-in audible alarm when the countdown reaches zero
  3. Countdown and Turn On - as above, but turning a device ON (with optional alarm)
  4. Continuous Intervals - the timer will continue to cycle between an ON duration and an OFF duration; the intervals can vary between 1 second and 59:59 minutes, or 1 minute and (I think) 23:59 hours. (This is what I'm using for my X10 workaround, resetting the X10 RF/AC interface every 30 minutes for one second.)
  5. Set Interval Periods (Daily) - this restricts the behavior of #4 above between defined Start and Stop times.
(There's a good chance that by the time you read this - originally posted May 2019 - this particular model won't be available, but I suspect you'll be able to find something similar. I just wanted to share that this kind of solution exists at all.)

I'm excited that these exist, and I suspect that I'll be acquiring a few more.

Thursday, October 25, 2018

Having to Scroll Horizontally to Read Your Gmail? Fix Gmail Message Formatting Caused by Large Images

This doesn't come up that often, but sometimes when I receive email with some kinds of large image files included inline with the body text of the email, Gmail presents the image in actual size, rather than scaling it to fit on-screen. When the image is very large, the image can display at several times the width of the region of the Gmail window for viewing message. Worst of all, Gmail flows the text of the message to the width of the image, requiring the user to scroll left and right to read the message.

This free Chrome extension fixes that behavior, configuring Chrome to automatically scale images to fit in the current message pane (as Gmail should have been written in the first place. Gmail's built-in image viewer is still accessible by double-clicking the image, so the user still has access to the full resolution of the inline images.

Gmail Inline Image Fit

Thursday, May 31, 2018

Batch Extract Image Files from PowerPoint Presentations

After going through a lot of grief with alternate (and unsuccessful) methods to do this task, I ran across this incredibly simple solution for extracting image files from within PowerPoint presentations. (I'm repurposing decades-old PowerPoint presentations with hundreds of images on hundreds of pages, so hand-extracting the content image-by-image, page-by-page is tedious and even physically painful.)

The only minimum requirement is that the PowerPoint files be in .pptx file format (not just .ppt), or access to a version of PowerPoint from Office 2007 or later, which can write .pptx files.

This example is on a Mac, but the same principle works on Windows, all that is required for Windows is an un-ZIP utility.

The solution is SIMPLE. SIMPLE.

  • If the PowerPoint file has a .ppt extension, open it in PowerPoint 2007+ and save it again as .pptx.
    • PPTX files save presentation data as widely-supported XML data structures, compressed in a package using the venerable ZIP archive format.
  • On a Mac, rename the .pptx extension to .zip. The Finder will ask if you’re sure. Click “Use .zip.”
  • Double-click the resulting .zip file. The Finder will uncompress the file into a directory structure. Inside[folder with orig filename]:ppt:media are all the image files in their native formats.