Image processing: png vs jpg: when they’re the same size….

Self-tutoring about image formats: the tutor shares a find.

In my post from June 6, I include a photo of a spider taken from my phone. I saved it both as a .png and a .jpg (aka,.jpeg), same dimensions, etc. I thought the .jpg file would be smaller (in memory) than the .png one. Interestingly, they are the same, at 55kB.

I researched how a .jpg and its corresponding .png image can be the same size. It turns out that, indeed, they can, and here’s the reasoning:

Both .png and .jpg use compression. The .png finds patterns among pixels, so compresses according to the predictability. The .jpg, on the other hand, potentially reduces the colour variety from pixel to pixel in ways the human eye may barely notice – if at all.

Therefore, just for an example, a photo entirely one single colour value might likely be compressed smaller in the .png than the .jpg format, since it’s absolutely predictable.

In its original application, .png does not allow for loss – meaning that if a pixel can’t be predicted, it’s recorded uniquely. Therefore, a .png image might need more memory than its .jpg counterpart. However, if the image processing software can find enough pattern in the image – and if the colors don’t show tremendous variety in the first place – then apparently a .png file can end up the same memory size as its corresponding .jpg – maybe even smaller!

I hope to post more about image formats:)

Source:

www.techradar.com

medium.com

stackoverflow.com

stackoverflow.com

Jack of Oracle Tutoring by Jack and Diane, Campbell River, BC.

Technology: what is bounce rate?

More self-tutoring about technology: the tutor shares the term bounce rate.

bounce rate
percentage of visits that view a single page on a site, then leave.

Source:

support.google.com

blog.kissmetrics.com

Jack of Oracle Tutoring by Jack and Diane, Campbell River, BC.

Computer technology: what is a hypervisor?

For me, understanding computer technology requires constant self-tutoring. The tutor defines the term hypervisor.

In my Feb 15 post I explain the idea of a virtual machine. The virtual machine exists atop a hypervisor.

hypervisor (noun):

a program that allows one or more virtual machines (VMs) to function from a single hardware entity. It may host a distinct instance of the same operating system to each VM, or perhaps even different operating systems to different VMs.

The hypervisor exists as a layer above the hardware but below the VMs. The users of the VMs needn’t be aware of the hypervisor.

Source:

www.howtogeek.com

www.networkworld.com

www.w3schools.com

Jack of Oracle Tutoring by Jack and Diane, Campbell River, BC.

Windows: file permissions: what does Bypass Traverse Checking mean?

Researching file permissions can mean self-tutoring. The tutor relays the idea of Bypass Traverse Checking.

Bypass Traverse Checking (file permission)

This permission allows a user to access a specific file that is not protected, but which resides in a folder the user does not have clearance to examine.

Under the Bypass Traverse Checking permission, the user can navigate to that specific file by its full path designation, without the operating system checking the user’s clearance regarding the containing folder. However, without the necessary clearance, the user cannot simply enter the folder.

Source:

www.pcreview.co.uk

docs.microsoft.com

Jack of Oracle Tutoring by Jack and Diane, Campbell River, BC.

Computer science, technology: what is a virtual machine (VM)?

More technology self-tutoring: the tutor explains the idea of a virtual machine.

virtual machine (abbreviation: VM):

An entity that is accessible via keyboard and screen, like a desktop, and may function, to the user, like a standalone computer. However, the virtual machine resides in a server or computer that may host many others as well.

In a simple case, each employee might use her/his own separate VM at work, but in fact all of the VMs might reside on a single server. (In reality there would likely be at least two servers for back-up purposes.) Yet, each employee experiences their own PC.

On the client side, the actual deployment of the virtual machines might be accomplished via network connectivity and login credentials.

Source:

azure.microsoft.com

www.lifewire.com

Jack of Oracle Tutoring by Jack and Diane, Campbell River, BC.

Computer science, technology: what is firmware?

Technology has its own terms which may require self-tutoring to understand. The tutor defines firmware.

firmware (n):

instructions that reside in a device for the purpose of performing its pre-set functions. Typically, firmware is device-specific and meant to operate without the user’s awareness. It can be updated in order to resolve performance issues or increase the device’s capability.

Firmware is programming that runs hardware. Routers and mobile phones, for instance, have firmware. A PC does as well: its firmware enables it to cooperate with the monitor, keyboard, disk drives, etc.

Source:

www.lifewire.com

www.lifewire.com

Jack of Oracle Tutoring by Jack and Diane, Campbell River, BC.

Technology, mobile phones: Nexus 4: .aux folder in DCIM

Using technology can lead to continual self-tutoring. The tutor mentions a fact he learned today.

Looking to download some photos from my phone to storage, I found a .aux folder inside the DCIM one. (DCIM means Digital Camera IMages.)

Wondering what the .aux folder contains, I opened it and found a single image relating to many others the kids took years ago while assembling an animation. Yet, why is it there, alone?

I discovered a similar photo to it in the main DCIM, alongside the others from that day. Yet, it’s from a few days later. It’s a mirror image of the one in .aux.

Apparently, when an image is altered, its original may (on some platforms) be stored in a .aux folder, while the changed one replaces its predecessor in DCIM. Such seems to be what happened in this case, anyway.

HTH:)

Source:

www.howtogeek.com

android.stackexchange.com

www.reddit.com

Jack of Oracle Tutoring by Jack and Diane, Campbell River, BC.

Medical technology: is CT scan the same as CAT scan?

Curiosity has led to self-tutoring: the tutor discusses the two terms CT scan and CAT scan.

CT scan and CAT scan have the same meaning. CAT scan is the older term.

CT stands computerized tomography, whereas CAT stands for computerized axial tomography.

Tomography: a method to produce pictures of internal body structures. Tomography acquires information from many cross-sectional scans.

Computerized tomography conveys the idea that, once the cross-sectional scans have been taken, a computer program is used to produce an image from their data.

In the phrase computerized axial tomography, the word axial refers to the idea that the cross-sectional scans are taken by revolution around a common axis (axis=line). Specifically, a scan is taken around the patient, then another a short distance along, and so on.

Source:

www.cancer.org

blog.cincinnatichildrens.org

Jack of Oracle Tutoring by Jack and Diane, Campbell River, BC.

Lifestyle, mobile phones: phone cases

Perhaps lifestyle requires more tutoring than anything else – for me, anyway. The tutor relays his experience phone case shopping.

Yesterday I got schooled on how to buy phone cases. I’m interested to share what I’ve learned.

We bought my son a phone that’s been out a couple of months. It’s an Android, a very good phone, but not flashy or brandy.

At a big-box store the clerk told us that, with more generic phones, cases are easier to get from a dedicated phone case seller. The big box places might stock cases for prominent brands and makes, but there are many others that they might not cover very strongly.

Therefore, we went to a kiosk in the Woodgrove Centre mall in search of a case for my son’s new phone. The kiosk is near Boathouse. We didn’t even have his phone with us – no problem. The attendant knew which one it was, and that it had been out for only two months. He had a few choices, including wallets. He also had screen protectors.

I chose a wallet case for my son’s phone, and also got him the screen protector. The attendant wanted to put the screen protector on for us, and told us if we brought him the phone, he would.

Just for kicks and giggles, we asked if he had a case for my phone – a Nexus 4. “Nexus 4?” he repeated. He uncovered a storage box, dug in, and pulled one out. I bought it. Here is my Nexus 4, in its new amazing case:

Jack of Oracle Tutoring by Jack and Diane, Campbell River, BC.

Web design: Div border on mobile phone: a possible solution?

Tutoring web design, mobile phones have their own demands. The tutor attempts to please them.

In yesterday’s post I discovered a border that showed up on my desktop but not on mobile.

Border?

 

Apparently the border-width needs to be set for a mobile phone to show it. This one is set to 2px.

Source:

w3schools

Jack of Oracle Tutoring by Jack and Diane, Campbell River, BC.