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.