COMP6021 Class 07.1

We looked at dithering.

We looked at dithering in Photoshop on a 10x10 pixel image. Students The student did some experiments with dithering in Photoshop.

This video might also be useful

COMP6021 Class 06.4

We used Photoshop to convert an image to indexed colour. Students downloaded various images and experimented with different settings [but didn't use dithering].

In the next class we will look at dithering.

COMP6021 Class 06.3

We looked at lossy compression, interpolation, and indexed colour.

COMP6021 Class 06.2

We looked at the RGB, Lab, and CMYK colour systems. I also mentioned Pantone

See also Capsure

This video may be of use

COMP6021 Class 06.1 Digital Colour

We began our look at colour and how it is represented.

Thine video may be of use

COMP6021 Class 34 Bayer Filter, Interlaced Video

the one with the electron gun

We looked at the Bayer filer used in sensors like those in cameras.

I explained how interlaced video works and we looked at some of its side effects.

COMP6023 DWEB1 Classes 27 & 28 Dithering lab

Students did a dithering exercise using Photoshop.

COMP6021 Class 27 Lab

We did some dithering experiments using Photoshop

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.

COMP6023 DWEB1/ITM1 Class 25 Indexed Colour and Dithering

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

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 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 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