Java Swing - Graphics
TOPIC 05 – IMAGE FILES PIXEL BY PIXEL

 

LESSON WORK

 


Your teacher will inform you as to how many marks you need to earn. 

 

QUESTION 1 – REMOVE COLOURS (3.5 marks)

 

Make an application that displays the same image four times.  Here is what each version needs to be:

  • Original image
  • Image with no red in it.
  • Image with no green in it.
  • Image with no blue in it.

 

 

QUESTION 2 – GRAYSCALE (4.5 marks)

 

Making an image grayscale can be done in many different ways.  The method that we looked at in the lesson is called the average method.  It consists of adding the original colour's red, green and blue colour values together and dividing by three – taking the average of the three.

 

Gray Amount = (R + G + B) / 3

 

Another method to create a grayscale image is called the lightness method.  In this case, we actually take the average of the highest of the three colours and the lowest of the three colours.

 

Gray Amount = ( max(R,G,B) + min(R,G,B) ) / 2

 

A third method, called the luminosity method, accounts for the fact that humans are more sensitive to green than to other colours.

 

Gray Amount = 0.21R + 0.72G + 0.07B

 

Create an application that displays a single image four times side by side.  One image is the original in full colour and the other three are in grayscale using each of the different methods described above.

 

<NO IMAGE AVAILABLE>

 

 

QUESTION 3 – REDSCALE, GREENSCALE, BLUESCALE (4 marks)

 

Recall the method to grayscale an image (using the average method).  Instead of applying the calculated amount to all colours in order to get a gray, you will now apply it to just one colour (and zero to the others). 

 

So, for a redscale, we use:

 

New Red = (R + G + B) / 3
New Green = 0
New Blue = 0

The same idea applies for GreenScale and BlueScale.

 

Create an application that is similar to the following below:

 

 

 

QUESTION 4 – ROTATE & MIRRORS (5 marks)

 

Create an application that will do a horizontal mirror, vertical mirror and 180 degree rotation.  You should achieve all of these by switching the colours of different pixels with colours of other pixels.

 

 

 

QUESTION 5 – INVERT (5 marks)

 

In this question, you will invert the colours of an image.  To invert a colour, we simply use the following:

 

New Red = 255 – Old Red
New Green = 255 – Old Green

New Blue = 255 – Old Blue

 

One can also add a little more complexity to the invert process.  One can specify the number to subtract from instead of using 255.   For example, invert192 will use the following:

 

New Red = 192 – Old Red
New Green = 192 – Old Green

New Blue = 192 – Old Blue
*Values below zero must be set to zero.

 

Create an application that shows an image inverted from 255, 192 and 128 like below.

 

 

 

QUESTION 6 – NEAREST COLOUR (6 marks)

 

The amount that two colours differ from each other can be called the distance between the two.

 

The distance between any two colours is calculated by adding up all of the absolute differences between the two reds, greens and blues.  Note that absolute difference simply means that we take the absolute value of the differences.

 

So, the distance between blue (0, 0, 255) and gray (128, 128, 128) would be 128+128+127= 383.  

 

And the distance between rgb colours (125, 16, 181) and (145, 120, 240) is 20+104+59=183.

 

To create a black and white image, we consider every pixel and figure out if it's closer to white or to black.

 

You will create an application that will examine each pixel's colour and replace it by the nearest colour available.

 

Image 2 colours:

·         Black (0,0,0)

·         White (255,255,255)

 

Image 3 colours:

·         Black (0,0,0)

·         White (255,255,255)

·         Gray (128,128,128)

 

Image 4 colours:

·         Black (0,0,0)

·         Red (255,0,0)

·         Green (0,255,0)

·         Blue (0,0,255)

·         Yellow (255,255,0)

·         Purple (255,0,255)

·         Teal (0,255,255)

·         White (255,255,255)

 

Here is an example:

 

 

 

QUESTION 7 – ROUND DOWN (5 marks)

 

One way to lower the number of colours in the image is to round individual red green and blue values to the nearest multiple of 10.  So, the rgb colour (132,45,193) becomes (130,50,190).

 

You will write an application that will do this rounding effect at three different levels.   Image 2 will round down to the nearest multiple of 25.  Image 3 will round down to the nearest multiple of 50.  Image 4 will round down to the nearest  multiple of 100.

 

Here is an example:

 

 

 

OTHER IDEAS

 

Colour mapping

Fading in and out

Random rectangles with effect applied to that rectangle only