Image manipulation lab

Manipulating images using arithmetic

Image filtering, enhancement and general manipulation using Photoshop

1)      Find the images on Moodle to be used in this lab and download on to your desktop.

2)      Click on All Programs->AdobeCreativeSuite4ProductionPremium and run Adobe PhotoshopCS4

3)      Use File\Open CH_Tor.jpg to display the image in Photoshop.

4)      Perform Image->Image Rotation->90 degrees CW

5)      Apply a custom filter to the image in the manner discussed in the lecture to filter the image as Filter->Other->Custom

Modify the default Mask to

   -1

-1 4 -1

   -1

What is the effect of the default mask? Why do you suppose that it creates the effect that you see?

Modifying the mask seems to change the image to black and white. In doing so it highlights straight edges with white lines and solid blocks of colour change into black.

6)      Experiment with various masks and explore the use of the preset masks in the High pass, maximum and minimum options. Where possible describe and explain what you see?

• When I increment the radius value of the minimum option the tower in the picture seems to expand and the colour is predominantly black, I think this increseases the size of all the pixels and the black block of colour from expanding black pixels masks the other colours.
  
  
  
  
• The effect of maximum option seems to be the opposite of the minimum one where it reduces the size of each pixel in the image, although it leaves a white outline, this is leading me to believe I was perhaps wrong about black masking the other colours and it's possibly just the opposite of this white outline effect.
  
  
  
  
• The high pass filter makes the outlines of the image glow and turns the blue sky to grey

7)      Suggest possible uses of this filter technique for processing digital photographs?
The most obvious use of filters is to add effects to a whole photograph without taking the time to edit it manually pixel by pixel, that you wouldn't get from taking a photograph, something that makes it look unique.
Since these filters seem to manipulate pixels maybe it can be used to improve the quality of images, perhaps something along the lines of anti aliasing to smooth out a jagged image.

8)      Create a new filter that is all zeros except for the centre value which should be 1. What does this filter do and why?

The filter doesn't change anything about the image, I suspect each 0 means 0 changes  to the image while the 1 in the middle means display the original image and change nothing about it, if I type 0 instead there it would not display anything.

How can you check that it operates as you think it does?
I just compared it with the original image and I see not difference

9)      Create a new filter with a two by two matrix of 1’s near it’s centre. What does this filter do and why?

This filter overly increases the intensity of light in the image this is known as saturation, some parts still remain dark, I think positive numbers in a custom mask amplify the intensity of light the higher that positive number is.

10)  Create a new filter with a two by two matrix with +1’s on one diagonal and –1’s on the other. What does this filter do and why?

Almost every block of colour in the image is turn to black, the outlines of the image are very faintly in white, I think because if you add all these numbers together they create 0 and if you just type in 0 on the filter the image will be covered in black completely, having 4 different numbers somehow lets the image keep its outlines.

11)

I used the colour halftone filter it converts the pixels in the image to a collection of coloured circles that emulate the original image.