Digital Graphics and Animation Processing Techniques
This section is more of a vocabulary list. If contains a list of methods that can be used when processing images and video. You will certainly want to include some of them in your designs: this list therefore contains many of the common processing techniques, definitions and the correct vocabulary to use when discussing them. Many also contain links for further information should you wish to read further.
Mathematical principles and processes
Algorithms
noun a process or set of rules to be followed in calculations or other problem-solving operations, especially by a computer.
For an extremely technical description of image processing algorithms, see here. (Note this information is purely optional and not part of the course)
Composite Transformations
A composite transformation (or composition of transformations) is two or more transformations performed one after the other. Sometimes, a composition of transformations is equivalent to a single transformation.
See a more in-depth description here.
Image arithmetic
Image arithmetic applies one of the standard arithmetic operations or a logical operator to two or more images.
See examples here.
Rotation (2D and 3D)
The input to an image rotation routine is an image, the rotation angle θ, and a point about which rotation is done.
However, note the uses beyond simply editing images. Again, a highly scientific and mathematical explanation is found here.
Scaling (2D and 3D)
In computer graphics and digital imaging, image scaling refers to the resizing of a digital image. In video technology, the magnification of digital material is known as upscaling or resolution enhancement.
Please note that vector images can be scaled with no loss of resolution, as you are simply moving the location of the nodes. This is not the case for raster images.
Translation (2D and 3D)
This refers to the mathematical process of translation, not the linguistic one. Mathematical translation refers to moving an item in either two or three dimensions.
Graphic processing – file size
Quality of Image
As already alluded to earlier, lossy compression results in throwing away some image data. Some compression algorithms, such as JPEG, allow the user to adjust the compression level to achieve a file size of their choice; the trade off is that as the file size is reduced, the image quality suffers.
See this page for a demonstration and explanation.
Frame Disposal
This approach utilises software such as Adobe Photoshop to reduce its file size through removing unnecessary frames which are declared unrequired for the final animation. It removes the current frame when the next frame is played. This restricts previous frame images from appearing in repeated frames. If this is initiated, then it will remove the previous frames after they have been played, thus reducing the time needed to play the frame as well as the overall file size, as less data needs to be stored at once. A disadvantage to using this is that it may remove frames that will be noticeable which means not the ideal method for high quality animations. (from here)
Auto Crop
Auto crop will crop an image to remove whitespace or other unnecessary detail from around the subject. This hopefully allows you to store a smaller image (fewer pixels) and potentially fewer colours (in the case of indexed colour) as you are only storing data on the part of the image that you want.
The only drawback of this technique is that there is a danger that the crop may remove some of the required image.
Compression formats and techniques
Image Compression
This has already been covered here and here but for more detail, and descriptions of how the techniques work, see here.
Video Compression
This has been discussed already but again, for more detail, and descriptions of how the various techniques work, see here.