Lesson video

Hi, my name is Mr. Hogan.

I'm so excited to be learning with you today.

We are going to have such a great time learning about data representation of images and sounds.

I will be supporting you with our learning during these lessons.

I'm so pleased that you have decided to complete your learning with me today.

We are going to do brilliantly.

Welcome to today's lesson from the unit "Data Representation: Images and Sounds." This lesson is called "Representing Images with Binary Data." By the end of today's lesson, you'll be able to explain how images are represented using binary digits and created using the RGB system.

I hope you enjoy it.

There are four keywords for this lesson.

Let's take a look at them.

We have pixel.

This is a single element of an image on a computer screen.

Bit, this is a binary digit.

This is the basic unit of data within a computer system that has a value of zero or one.

RGB system, this is a colour model used to represent and create colours by combining three colours of light: red, green, and blue.

And the last key word is intensity.

This is the strength of a colour shown by the value of each element: red, green, or blue.

So the lesson outline for today, so it's split into three parts.

The first part is describe how images are formed of pixels.

Then we go on to describe how an image can be represented as bits.

And finally, moving on to combining red, green, and blue colours.

It's going to be a great lesson.

I'm really looking forward to it.

Let's start with describe how images are formed of pixels.

Have you ever taken a photograph on a digital device such as a phone or a camera? How does that device capture the image? Alex is asking, "How does the camera know how to store that image?" Laura is also asking, "What steps does the computer take to display that image?" Interesting questions that we hope to answer.

Digital images are composed of individual elements arranged in a grid.

The elements of a digital image are called pixels.

That's short for picture elements.

The pixels are displayed on the computer or device for you to view the image on.

So you can see we have a little game character on the right-hand side here, and the individual squares or individual elements that look like squares, they're called pixels.

When you zoom in or enlarge an image, the pixels are stretched into larger blocks.

So where we've zoomed in on this hummingbird, you can see that individual blocks that are pixels.

That's why images appear poor quality when you enlarge them too much, like this astronaut example where we zoomed in on their leg.

The images that play blurry or blocky, this is known as pixelated.

So you can see on this example, this animation, when we're zooming in, you can see it becomes like blurry and pixelated.

Let's have a quick check.

What happens to the pixels in additional image when you zoom in or enlarge it? As it's A, the pixel stay the same size, but more pixels are added to fill the space? Is it B, the pixels get stretched and become larger, making the image look blocky or blurry? Or is it C, the pixels change colour, making the image look distorted? Take your time.

Remember, you can always pause this video or even rewind it to previous slides to look at the answer.

Shall we have a look at the answer? It is B, the pixels get stretched and become larger, making the image look blocky or blurry.

Remember, this is known as pixelation.

Well done on getting the answer right.

If you didn't get the answer right, don't worry.

We carry on the lesson, and I'm sure you'll enjoy it.

This image is a grid of 12 by 12 pixels.

It contains six red pixels on, like, the tongue of the smiley face, 20 black pixels, so that's the eyes, the winky eye and the mouth, 86 yellow pixels, so that's the remainder of the face, and 32 white pixels.

Don't forget about them.

They are in the background of the image.

Let's have a quick check.

This image is made up of 132 pixels.

Which of the following is true? A, there are equal amounts of white and black pixels.

B, most of the pixels are blue.

Or C, there are 21 white pixels.

So you can pause the video at any time or rewind it if you want to to look at previous slides.

But probably you need to pause this one because then you need to do some counting.

Shall we have a look at the answer? It is C.

There are 21 white pixels.

So hopefully you counted those individual pixels.

Well done.

Let's have a practise now.

One, what are the tiny squares that make up a digital image called? Two, why may an image look blurry or blocky when you make it larger? Remember you can pause the video at any time or rewind it.

Let's have a look at an answer.

So one, what are the tiny squares that make up a digital image called? So the tiny squares that make up a digital image are called pixels.

Two, why may an image look blurry or blocky when you make it larger? So an image looks blurry or pixelated when you zoom in too much because the pixels are stretched and become large and blocky.

Hopefully you got these answers right.

Well done.

We're going to move on to the second part of the lesson.

Describe how an image can be represented as bits.

So we've looked at pixels.

Now we're gonna see how this actually is represented in bits.

Each pixel is assigned a binary number that represents a specific colour.

This black and white smiley face can be represented using just one bit per pixel: zero for white pixel and one for a black pixel.

So if you put those into the image, you can see that for every black pixel it is represented by a one.

And for every white pixel, it's represented by zero.

So we are using one bit to represent it.

Let's have a quick check.

How many different colours can one bit represent? Is it A, one; B, two; or C, four? Remember, pause the video at any time or you can rewind it to the previous slide.

Shall we have a look at the answer? It is two.

There are two combinations of a single bit, one and zero.

Laura is asking, "So one bit is used for an image with any two colours.

The first colour can be one and the zero can be the other colour." Alex is questioning, "Yes, I understand that, but there are more than two colours in most images.

How does that work?" Let's move on and see if we can answer Alex's question.

Two bits can represent four colours.

Each combination of two bits can represent a colour.

So here we have 00 for white pixel, 01 for a yellow pixel, 1-0 for a black pixel, and 1-1 for a red pixel.

So putting those binary digits into the image, you can see that we have four colours represented by two bits.

Let's have a check.

This pointer on the white background uses three colours.

How many bits are needed to represent each pixel in this image? Is it A, one; B, two; or C, three? Remember, pause the video anytime or even rewind it to replay parts.

Shall we have a look at the answer? It is B, two.

Although only three colours are used in the image, two bits are required because the image contains more than two colours, and two bits can represent up to four colours.

So yeah, it needs two bits even though there are only three colours in the image.

Hopefully you got that answer right.

Well done.

We're gonna have a practise now.

One, the top row of this image contains two colours.

How many binary digits, bits, are required to store this row? Two, how many bits are required to store the colours in the whole image? Three, if you add a blue border, one pixel y to the image, how many bits will now be required to store the image? Four, why does using more bits per pixel allow you to have more colours in an image? These questions will take maybe a bit of time to answer.

So please pause the video and remember to rewind it if you want to recap on anything.

So possible answers, one, the top row of this image contains two colours.

How many binary digits, bits, are required to store this row? So if you are just storing this row, there are only two colours on the top row.

So this could be represented with a single bit.

So we've just put the binary number in the top row to show you of one and zero, representing black and red.

Two, how many bits are required to store the colours in the whole image? So there are how many colours in this image? One black, two red, three white, and four blue.

So therefore it is two bits, as you can see in the image now.

If you add a blue border, one pixel white to the image, how many bits will be now required to store the whole image? It would still be two because the colour blue has already been used in the image.

So no more bits are required.

Four, why does using more bits per pixel allow you to have more colours in an image? Well, each bit can either be a zero or a one.

Therefore, increasing the number of bits expands the possible combinations of ones and zeros.

Each unique combination can represent a different colour, enabling a greater variety of colours in the image.

Well done for getting this far.

Hopefully you're enjoying it.

I'm really, really enjoying it myself looking at different ways that images can be represented as bits and I've learned about pixels and images being pixelated.

Well done.

We are going to be moving on to combining red, green, and blue colours.

Computers create a variety of colours by mixing different amounts of three colours: red, green, and blue.

Overlaying these colours allows new combinations of colours: yellow, cyan, and magenta.

This is known as the RGB system.

So you can see on the animation that when these circles of red, green, and blue combine, where they overlap, they form different colours of yellow, cyan and magenta.

Let's have a check.

In the RGB system, which colour is created by combining red and green light? Remember, you can pause the video at any time, or if you want to go back and have a look at the previous slide to see if you can find the answer, please do that.

Shall we have a look at the answer? It is yellow.

Yeah, so now you, you can see the animation on this slide where you can see the red and green overlapping.

Now, it forms yellow.

Colour intensity is measured on a scale from zero to 255 for each of the colours, the red, green, and blue.

Zero means none of the colour is present.

255 is the most intense colour possible.

For example, zero of the red, 255 of the green and zero of the blue represents green because the green is set to the highest intensity and the red and blue are not used at all.

So you can see on the image where we have a similar pattern representing red 255, 0, 0; and blue, 0, 0, 255.

You can now see all the other colours and their intensities represented as RGB values.

The values of intensity to create the colour blue are zero for red, zero for green, and 255 for blue.

The values of intensity to create the colour cyan are zero red, 255 green, and 255 blue.

You may remember the green and blue crossing over in the animation, and that provided the cyan colour.

The colour taken from this pixel has the following intensities: 255 for red, 187 for green and 100 for blue.

So if you put these intensities together, it gives this colour of the kingfisher's breast.

When the colour changes, the values change.

So for this kingfisher's wing, which is sort of a light blue, it's represented by the intensities of 87 red, 165 green and 235 blue.

Let's have a check.

In the RGB system, what does a colour intensity value of zero indicate? Is it A, the most intense version of that colour; B, a medium intensity of that colour; or C, none of that colour is present? Remember, you can rewind this video at any time or pause it to have a think about the answer.

Shall we have a look at the answer? It is C.

None of that colour is present.

Well done if you got that right.

And if you didn't, don't worry.

Take some time, maybe rewind and have a look at the other slides again.

Practise time, so question number one, what are the three colours that computers use to create other colours? Two, how do computers create different shades of a colour? Three, what RGB values would you use if you want to create a red pixel? Four, what RGB values would you use if you want to create a yellow pixel? Remember you can pause the video at any time and go back to previous slides.

Let's have a look at some answers.

Question one, what are the three colours that computers use to create other colours? So it's red, green, and blue.

Two, how do computers create different shades of a colour? So computers create different shades of a colour by changing the intensity of red, green, and blue.

Three, what RGB values would you use if you want to create a red pixel? So you have 255 on the red, the greatest intensity it can have, zero on the green, and zero on the blue 'cause that is no intensity at all.

Four, what RGB values would you use if you want to create a yellow pixel? So you'd have 255 for red, 255 for green, and zero for blue.

So when red and green combine, like we saw on the animation, it forms yellow.

Well done.

You've come to the end of the lesson.

You've done so well.

I've really enjoyed learning with you today.

So in summary, you've learned that digital images are made up of tiny squares called pixels and it's arranged in a grid.

Computers use bits, ones and zeros, to store and display images.

The number of bits required depends on the number of colours the image is made of.

And also each pixel's colour is a mix of red, green, and blue.

Well done.

I've really enjoyed learning with you today.

Thank you very much.