Lesson video

Hi, I'm Dorini.

Welcome to lesson one on data representation, going audio visual for this lesson, you will need pen and paper and some colouring pens or pencils for your task.

Remove any distractions.

If you can, and turn off those mobile notification, especially if you have your devices nearby, when you're ready let's crack on.

in this lesson, you will describe how digital images are composed of individual elements.

You'll be able to recall that colour of each picture element is represented as a sequence of binary digits.

You'll be able to define the key terms, pixels, resolution, and colour depth.

You'll be also able to describe how an image can be represented as a sequence of bits.

Why the title is Binary Mosaic, similar to Greek and Roman Mosaics, which are formed of individual pieces of glass or stone.

Digital images are formed of individual picture elements.

And they are represented in binary and hence the lesson title is Binary Mosaic, which is all about digital images.

Your first task for this lesson is Binary mosaic, to create a Binary mosaic.

It involves two steps.

Step one, you create a picture from individual elements.

Step two, you use one or two binary digits to represent the colour of each element.

Here's an example to understand what you have to do.

So step one, you create a picture from individual elements.

You can clearly see here is a rectangular grid with different number of squares and it is coloured to create a picture.

And what do you think that picture is? Yes.

Emoji.

That's correct.

So you can use one or two or up to four different colours in a picture.

You can use grids as largest 16 by 16, or you can use as more or less eight by eight, or you can use only part of the squares within the rectangular grid, like 12 by 13 on a 16 by 16 squares.

So that's entirely your choice.

What you cannot do.

You cannot leave picture elements without a colour.

And the second point is you cannot use more than one colour within an element.

That is within a single square.

You cannot mix colours.

Every square has to have a single colour.

Here's an example of a binary mosaic that four different colours.

So what colours can you see? Yes, absolutely.

It's white, green, yellow, and red.

Those are the four colours represented in this binary mosaic.

So as part of doing your first step, that is creating a picture from individual elements.

You can choose any grid.

You can choose a smaller grid like eight by eight, or you can choose a larger grid like 16 by 16, and you can choose one or two, of up to four colours.

With your step two, for the creation of binary mosaic, you have to use one or two binary digits to represent the colour of each individual picture element.

So what you can do as part of your step two, you can decide whether to use a single binary digit or a pair of binary digits and to correspond to which colour.

What it cannot do is use one bit for some colours and a pair of binary digits , for other colours, you cannot do that within a single picture.

Let's see how to represent using binary digits for four different colours.

So now you're representing four different colours.

So the number of bits we use has to be two, so we can have four different combinations of the numbers.

So the four different combinations are zeros zero zero one, one zero and one one.

Now look at the picture carefully on your right hand side.

what are the binary digits used to represent a red colour? 11 that's correct.

Absolutely correct.

So what about yellow? Zero one.

That's correct.

We have used a pair of binary digits to represent colour of each individual picture elements.

So now have you know, your first step in creating a binary mosaic is creating a picture using individual picture elements that is colouring every square on the rectangular grid.

What you can do is you can choose any size grid.

What you cannot do is colour every square with different colours.

So you got to use a single colour for every square.

You cannot mix the colours.

And what you cannot do is leave any square blank without any colour.

Step two, you represent every colour of the individual picture element using binary digits.

You can use a single digit or a pair of binary digits.

Now pause the video go and do your work sheet and come back when you're finished.

Welcome back.

Pixels.

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

This exactly the same, what you have done.

Video activity.

So in your activity, you have coloured every square on the rectangular grid.

So digital images are also composed of individual elements, and they are arranged in a rectangular grid, the elements of a digital image are called pixels , picture elements.

Let's see an example of a picture element of the bird.

It's a single pixel.

So let's do a bit of reflection of your binary mosaic activity.

Can you calculate how many bits you used to represent your entire image? How would you do that? Let's look at an example.

Here's a picture of an arrow.

So when you're calculating, how many bits needed to represent an image, the first thing you do is count the number of rows times, the number of columns.

So how many rows and columns does this picture have ? Row 14 rows and eight columns.

So the total number of pixels or 14 times eight, 112 pixels.

What other information do you have about this picture? You can see another bit of information in this picture is the use of colours.

We have used two colours, so we need to represent each picture elements, colour that is pixels colour using a single binary digit.

I used one bit for the colour of each pixel, so it can be on or off.

So when it is off, it's white colour, that's why you see the zeros.

And when it is on it's the green colour.

That's why you see the lot of ones.

The total number of binary digits for this image is 112 pixels times, one bit per pixel.

That's the colour depth we use.

So the total number of binary digits, or 112 bits.

What about this one? Can you calculate how many bits used to represent the entire image.

First calculate the number of rows times columns that will give you the number of pixels for that image? So how many doors have we got? Yes, Correct.

10 by 10.

So we've got 100 pixels for the image.

But how many colours have we used? Three? No, it's four colours.

So we have used four colours, including the white.

So to represent the colours, we need to use two binary digits.

So we have used zero zero to represent white , one one to represent the dark brown, zero one to the peach colour.

And the light brown is one zero.

So we have used four different colours.

So I have used two bits for the colour of each pixel.

So that will be 100 pixels, times two, that will be 200 bits.

So we need 200 bits to represent this image.

So Digital Image Representation.

When you did the activity about binary mosaic.

You represented images as a sequence of binary digits.

That's your step two.

That you have to represent each individual colour as a single binary digit or a pair of binary digits.

So let's look at the terminology.

Pixels and Resolution, a digital image is composed of individual elements arranged in a rectangular grid, similar to your binary mosaic activity, the elements of a digital image are called pixels or picture elements.

So pixels are nothing but individual elements of a digital image.

The number of pixels in a digital image is the image resolution.

So pixels refer to individual picture elements of a digital image and resolution refers to the number of pixels in a digital image.

Look on the right hand side an image of astronaut.

And the astronauts image has a resolution of 8,100 pixels.

So let's recall the fact again, Pixel refers to individual elements of a digital image and resolution refers to the total number of pixels in a digital image.

So the right hand side, you can clearly see the picture of the astronaut is slightly blurred.

It could be because of the resolution.

Let's see another picture to compare with.

So pixels and resolution.

Pixels refers to the individual picture element of a digital image and resolution refers to the total number of pixels in a digital image.

Under the astronaut image, you can see on the right hand side, but this time we have a higher resolution and the resolution is double the time before.

So it was 90 before, 90 times 90, and now the resolution has increased.

It has doubled so 180 times 180, 32,400 pixels.

Look at the quality of the image.

What do you think about the quality of the image? Do you think it is actually quite good with the increased resolution? Have a think about that.

So let us understand the advantages and disadvantages of images with high resolution.

Images with high resolution, that is a large number of pixels are great because increased quality, increased ability to capture detail.

You will be able to clearly see the picture, just like the astronaut picture, where you have used higher resolution.

That means large number of pixels.

That means you are able to see the.

You were able to capture the details of the picture.

So it increases the quality.

But remember the binary mosaic, if you use the larger grid, it's not so great.

Why? Because of the increased representation, because you need more space for storage and more effort required for processing the time you took to colour every square and more time required for transmission.

So converting the colours for every individual element to zeros and ones, it requires more time.

So images with high resolutions are great because of the increased quality, you will be able to capture the details of the images, but it's not so great because it requires more space for storage.

It requires more time for processing and transmission.

Colour Depth.

For every pixel a sequence of binary digits represents its colour.

So this was your step two.

So step your step two for the activity is to represent every individual pixel with the binary digit to represent its colour.

The fixed number of binary digits used to represent each pixel colour is the colour text.

Colour depth refers to the number of binary digits used to represent pixels colour On the right.

You can see the picture of astronaut in black and white.

The resolution of that image is higher.

So you can clearly see 720 by 720 that's 720 rows by 720 columns.

So you got about 518,400 pixels.

And it's colour depth is one bit because all you need is two possible colours, either on or off.

So for every pixel, a sequence of binary digits is assigned to represent its colours.

The number of binary digits used to represent the colour of the pixel is the colour depth.

Let's look at another example , there you've got four different colours.

So two binary bits have been used as its colour depth.

The resolution of the picture hasn't changed.

We have still kept the same high resolution, but colour depth has increased by two.

So we can represent four possible colours , using two binary bits.

Here is another picture bit three bits as colour depth.

So with two power three, that is eight possible combination of colours can be used to represent the picture, which is better than just four and better than even better than two.

Okay.

So the three bits as colour depth, you can represent eight possible colours.

So you can clearly see resolution is the same for the last three pictures, but the colour depth has increased from two four and eight and this increase in colour depth, we can clearly see the details in every picture with the different colours used.

So what are the advantages and disadvantages of images with high colour depth, lets recall, colour depth is nothing but the number of binary digits used to represent pixels colour.

So images with a higher high colour depth means a large number of bits representing each pixel colour.

That's great, because it can have more colours.

So with one bit you represent two colours, the two bits, four colours, three bits, eight colours.

So if there are any bits in an any picture it's two power, okay, so you can have high colour depth means , you got, you can represent more colours, which are great because we've increases the quality.

But remember the binary mosaic , why use two bits, for colour instead of one bit, why can't we use just one bit instead of two bits, it's not great because of the increased representation size, more space required for storage, more effort required for processing and more time required for transmission.

So if you think about, if you consider the advantages of high colour depth is increased quality, you can represent many colours , depending on the number of number of binary bits assigned for colours, but it's not so great because of the increase due to the increased representation size, most spaces required for storage.

So think about eight possible colours.

You need to have eight different storage spaces to store every colour, more effort required for processing and more time required for transmission.

So the terminology.

Digital images that are formed using binary representation of each pixel.

So the activity you'd done, the binary mosaic, those pictures are called bitmaps or raster images.

So digital images that are formed using a binary representation of each pixels colour are called bitmaps or Rasta images.

So your binary mosaic activity helped you create bitmaps or raster images, but there are variations to this thing, but this is one of the most common representation.

So look at this picture, can you see the quality increased quality? We have kept the same resolution, 720 by 720 , 518,400 pixels.

But what has changed is the colour depth.

So we are using 24 bits to represent all possible colours.

But remember.

There is also an alternative to bitmaps or Raster images, which takes a completely different approach using geometry shapes.

And it's called vector graphics.

Don't forget, there's a quiz at the end of this lesson, I would love to see your completed binder design.

So if you would like to share your work with Oak National, please ask your parent or carer to share your book on Instagram, Facebook, or Twitter, tagging @Oak national and #learnwithOak.

Hope you enjoyed this lesson.

See you in lesson two.