Activities‎ > ‎Investigations‎ > ‎Digital Images‎ > ‎

The Color of a Pixel

Each pixel displays the color of a tiny region of the image, and that color is the average color for the entire tiny region. In the following tables you will look at the red, green, and blue intensities of a large pixel and the smaller pixels that define the same region.

Materials

    DigitalImageBasics software can increase and decrease the resolution of the image, so that you can see how many pixels are necessary to recognize the picture’s subject.

    Download the software as part of the DEW software bundle
    Consider downloading the demonstration version since it includes 10 mystery pictures included in the programs interface.

    Download mystery images if you don't use the demonstration version (stuffed or zipped).

    Same as that used in Pixel Count

What To Do...

  1. Open a mystery picture of your choice in the "Pixels
    window of DigitalImageBasics.

  2. With the resolution at the minimum, 2x2=4, move the cursor over each pixel and write down the color intensity values shown in the lower left corner of PixelView.

  3. Increase the resolution of the picture to 4x4=16. This time write down the color intensity values for the four pixels that cover the same region as the Lower Left pixel from the 2x2 resolution. In the last row, write the average value of the column.


2x2 pixel resolution
UL
UR
LL
LR
Pixel
Red 
Intensity 
Value
Green
Intensity 
Value
Blue
Intensity
Value
Upper Left (UL)      
Upper Right (UR)      
Lower Left (LL)      
Lower Right (LR)      

 

4x4 pixel resolution
1
2
UR
3
4
LL
LR
Pixel
Red 
Intensity 
Value
Green
Intensity 
Value
Blue
Intensity
Value
UL-1
     
UL-2
     
UL-3
     
UL-4
     
Average Intensity
     

 

Question: Compare the averages from the second chart to the values for the Upper Left pixel from the first chart. How are they alike? What do you expect would be average intensity values for the pixels in this same region if the resolution is 8x8?

Finally...read about Color in Digital Images.

Effect of pixel size on an aerial photograph made  using a digital camera carried aloft with a kite.

Image with 2x2 pixels (no resolution)

Image with 8x8 pixels (still can't see what it is)

Beginning to see the outline of a bush, but still impossible to distinguish detail (32x32px)

Starting to see a real bush with some detail (128x128px)

Finally an accurate representation of a bush (512x512px)