COMP6021 Class 26 Transparency & PNG

We looked at transparency, alpha channels, and PNG.

[due to a technology failure there is no recording of today's class. The (shockingly similar) class above is from four years ago.]

COMP6023 DCOM1b Classes 27 & 28

We did some experiments with dithering in Photoshop.

COMP6023 ITM1 Classes 27 & 28 Lab

We did some experiments with dithering in Photoshop.

COMP6021/COMP6023 Animated GIFs Documentary

COMP6021/COMP6023 JPEG

Here's an online video I made some time about about JPEG. It is largely the same as what we did in class.

This rather unusual logo has it origins in the way JPEG works.

COMP6023 DNET1 Labs

For the remaining 6 weeks of the semester the DNET1 labs will be taken with James O'Sullivan. I will still see students in the lectures.

COMP6023 DNET1/COM1c Class 26 GIF & JPEG

We looked at GIF & JPEG image formats.

[no recording due to technical problems]

COMP6021 Class 25 GIF & JPEG

the one with the DCT

We looked at the main features of the GIF and JPEG image formats.

COMP6023 DWEB1/ITM1 Class 26 GIF & JPEG

We looked at the main features of GIF & JPEG.

Students now ave everything they need to complete Assignment 2.

COMP6023 DWEB1/ITM1 Class 25 Indexed Colour and Dithering

We looked at indexed colour, colour palettes, and dithering.

COMP6023 Essay title errors and omissions

Today I corrected any errors in the essay choices of which I was made aware.

Students may no longer chose a topic. That choice was made for them some time ago.

However, if you made a choice, advised me of it, and the list does not reflect that please let me know and I will try to find the e-mail you sent me.

Please check the list to ensure that the blog URL and essay title are correct.

COMP6023 DCOM1 Class 25 Subsampling, Indexed Colour & Dithering

[no recording today]

We looked at subsampling and interpolation. We saw how 24 bit images can be coded with fewer bits per pixel by using a well chosen palette. We played a palette matching game.

I explained how dithering works and students did an exercise on dithering. There are more such exercises in the notes, for students interested in doing more.

COMP6021 Online Class: Dithering

COMP6023 DNET1/COM1c Class 25 Dithering

We looked at dithering. [no recording]

We did an exercise in class. There are other similar exercises in the slides.

I answered a few questions about interpolation.

COMP6023 DCOM1 Class 24

We looked at the Lab and CMYK colour systems.

We finished a bit earlier than usual. I wasn't keeping an eye on the time. It felt longer. I guess I was tired :-)

COMP6021 Class 24

the one with Colin's tie

We looked at indexed colour palettes and at dithering.

Only 5 students were in class.

COMP6021 Online Class: 1-bit images

COMP6021 Compression

COMP6023 DWEB1 Class 23 & 24

Students worked on their blogs and on assignment 2.

COMP6021 Class 23 Lab

We looked at an images RGB, CMYK, and Lab channels using Photoshop.

Students converted images from RGB, to Lab and then subsampled the a and b components so that they were a mere 1/36th of their original sizes. The results were surprising good in most cases.


In these images 35/36ths of the colour information has been discarded. Look closely to see the impact of this.

Original PNG.

Subsampled Colour.

If you were on holidays and paying roaming fees to upload the picture you would would pay 3.00 for the full quality picture, but only 1.05 for the low quality.

COMP6021 Class 22

We looked at the Lab system and the CMYK system. The Lab system was interesting because it separates out the luminance and chrominance components of a image. We say how subsampling the chrominance components of an image can be quite successful.

We considered the use of subsampling as crude compression mechanism and looked at interpolation to replace the lost data.  in practice, interpolation is more complex that I explained.

COMP6023 DCOM1 Class 23 & 24

Students worked on their blogs and on assignment 2

COMP6023 ITM1 Class 23 & 24

Students worked on their blogs and on assignment 2

COMP6023 Add author to your blog

For this weeks blog post students are expected to guest post on someone else's blog. To allow someone to be an author on your blog, you must first invite them.

Take care not to make your guest an Administrator of your blog. That will give him or her total control. Author is enough.

COMP6023 Assessment Update

Essay

If you didn't send me your choice of essay title, one has been assigned to you. You can check the blog list to see what you got.

If you don't like the title you were assigned you will not be assigned another. There was plenty of time to make a choice. If you believe that you sent me your choice some time ago, and that I missed it, let me know and I will have a look.

This part of the process has taken so long that submission of a draft will not be compulsory. However it is still recommended. Details of how to submit will follow soon.


Blogs

I propose to begin correcting the blog posts for week 2-5 this week. If you need to correct errors and omissions in those weeks you have very little time in which to do so.

COMP6023 DNET1/COM1c Class 22

I did a quick recap of HSB, RGB, Lab

We looked at CMYK.

We looked at Indexed colour and palette selections for different images.

COMP6021 Class 21

the one with all the colours

Image digitization

HSB
RGB

COMP6023 DWEB1/ITM1 Class 22

We looked at some more at the RGB colour system. Then we examined the Lab colour system and saw how subsampling the colour comment of an image was not as noticeable  as subsampling the luminance component.

We looked at the CMYK system used in printing.

[Recoding failed]

I spoke a bit about image compression. I explained image subsampling and interpolation.

We began to look at pixel depth reduction when my laptop failed. We will pick up again from this point in the next class.

COMP6023 DWEB1/ITM1 Class 21

We looked at digitising black & white images and considered the impact the sample rate (dpi) and number of quantisation level (bit per pixel) have on the quality.

We looked at the HSB & RGB colour systems

COMP6021/COMP6023 Image Submampling

When an image is subsampled the missing pixels have to be accounted for by the receiver. This can be accomplished by increasing the size of the pixels that are present, or by interpolating the missing pixels. The different is illustrated in these images. You need to click on them to see them at full size.

COMP6021 Online Lesson - Digitization

We are currently considering how real world things are digitised. This video might be useful.

Digital Colour

This week in class we will be looking at how colour is represented digitally. This video explains the Hue Saturation Brightness (HSB) system.

This video outlines the Lab and CMYK systems.

COMP6023 Google Spam Detection: What is a "paid link"?

What's a "paid link"?

COMP6023 Google's Search Spam Dectection

Last week we spoke a little bit about Google's spam detection. Here are two interesting discussions about that work.

What's it like to fight web spam at Google?

COMP6023 DCOM1 Class 21

We looked at digitising grey scale images an looked at coding colour. I explained the HSB and RGB colour systems.

We will look at the Lab system in the next class.

COMP6023 DNET1/COM1c Class 21

We looked at digitising grey scale images an looked at coding colour. I explained the HSB, RGB, and Lab colour systems.

COMP6021 Online class: Image Digitization

COMP6021 Online Class: Subsampling & Interpolation

COMP6023 DCOM1A Timetable Change

COMP6023 Lab DCOM1A Monday 1600-1800 will be in C134x from now on. Students will discover Photoshop there.

COMP6023 DCOM1 Class 18

SEO
Analytics

COMP6021 Class 20

the one with the thermometers

We looked at Digitisation and saw how both the number of quantization levels and the sample rate can affect the fidelity of the digital representation of the analogue values.

COMP6023 Interesting Job Ad

http://www.irishtimes.com/jobs/featured-position-cpl/digital-marketing-manager-1.1705239

Note the requirement for SEO knowledge in this current job ad.

COMP6021 Class 19 Lab

Students saved GIFs with various settings for use in the assignment.

COMP6021 Class 18

the one with the LZW

We looked at Lempel-Ziv-Welch coding.


Students worked on an LZW exercise. The answer was Ando Masahashi

I did a Huffman coding question on the board from a past exam paper.

COMP6023 DOM1B Classes 19 & 20

Students worked on generating the GIF data required for Assignment 2.

COMP6023 ITM1 Classes 19 & 20

Students worked on Assignment 2 by saving the images as GIFs with different numbers of colours, with and without dithering.

COMP6023 DNET1 Classes 19 & 20

Students saved the GIF images they needed for Assessment 2.

COMP6021 Class 17

the one with the Huffman coding

We began our look at compression. We discussed lossy vs. lossless compression. we took a look at Run Length Encoding, Difference Coding, and Huffman Coding.

COMP6023 DWEB1/ITM1 Class 18

We looked some more at SEO and I showed students Google Analytics data from my blog.

(We got up to Slide 64)

[No recording of this class because I can't record classes back to back]

COMP6023 DWEB1/ITM1 Class 17

We began our look at SEO.