→Converting Between Types
=== Number of Colours ===
The size of the image can be reduced by reducing the number of bytes required per pixel. A PC can effectively display up to
4 bytes per pixel, split as follows:
* 1 byte for red
* 1 byte for green
| PNG || Loss of transparency flag || Lossless || Lossless || Loss of colour and transparency
| JPEG || Lossless || Lossless || Lossless || Lossless
Converting from JPEG to one of the other formats is lossless, but re-encoding it as a JPEG is lossy, so converting it back to JPEG will result in a different image than the original.
== Scanning and OCR ==
Text in a raster image is not the same as the same text in a text file. To convert rasterised text to computer text OCR is needed. The quality of current systems isn't that great.
== Degree Students ==
The point of using layers is that you can combine them into one image but still make changes to the individual components. This is a very powerful tool mostly used by graphics experts but it's useful even for some simple tasks.
= Lab =
This is a marked lab. Please submit it using Moodle (
== Gimp ==
* The Gimp on the lab machines isn't fully installed so it may take a very long time to start up the first time.
* Find a JPEG photo online, with width:height
ration of 4:3. The contents don't matter - mountains, trees, flowers, sky, whatever. For exmaple something from http://amdwallpapers.webspaceforme.net/gallery/ Save the image as step1.jpg
* Open the image with Gimp. Notice that most likely you're seeing a scaled down version, the zoom level is displayed at the bottom of the window.
* Resize the image to
900x720, save the result as step2.jpg
* Crop the step2.jpg so that you end up with a square 720x720. Do not scale the image, the proportions of the content should stay the same. Note: gimp has a menu option to do this. Save the result as step3.jpg
* Save step4.jpg as step4.bmp. Note how much bigger the bitmap is.
== Dia ==
* Download and install Dia.
* Draw your family tree (it doesn't have to be real, just different from other students) in Dia using shapes (perhaps boxes), arrows from children to parents, and lines without arrows between spouses. Change the colours for males to be blue (boxes and lines) and red for females.
== Submission ==
After doing all the steps above submit the following files to Moodle (
Lab2): step1.jpg, step2.jpg, step3.jpg, step4.jpg, family.dia, family.png, and one of the grayscale images generated by the last step.