Understanding Digitization, Compression, and Image Editing

Posted on Feb 4, 2025 in Arts and Humanities

Digitization

To convert analog information into digital data that computers can handle. This is a 2-step process:

Sampling
Quantization

Sampling

Analogous to weighing and recording a puppy’s weight.

During the sampling step, you need to set a sampling rate.

Sampling rate: How often you take a data sample.

Quantization

Analogous to rounding the weight to a fixed number of digits in the weighing puppy scenario.

During the quantization step, you need to set bit depth.

Bit depth: Refers to the number of allowable levels you map (or round) the values to.

Disadvantages of Large File Size

Takes longer to copy the file from one computer to another.
Takes longer to send the file over the Internet.
Takes longer to process (such as during opening and saving) the file.

Compression

File compression means techniques to reduce file size.

Two categories exist in terms of whether the data get lost during the compression:

Lossy compression
Lossless compression

Trade-offs of Reducing File Size

Data will be lost or altered when you apply these strategies:

Reduce sampling rate
Reduce bit depth
Apply lossy compression

When data is lost or altered, you sacrifice the exactness of the media’s original information. This affects the quality of the media.

Pixels

Each peg hole on a pegboard is a sample point.

The sample points are discrete.

In digital imaging, each of these discrete sample points is called a picture element, or pixel for short.

Sampling Rate in Digital Images

Refers to how frequently you take a sample.

For an image, sampling frequency refers to how close neighboring samples are in a 2-D image plane.

Resolution in Digital Images

In digital imaging, increasing the sampling rate is equivalent to increasing the image resolution.

Consequences of Higher Resolution

With higher resolution:

You have more sample points (pixels) to represent the same scene, i.e., the pixel dimensions of the captured image are increased.
The file size of the digitized image is larger.
You gain more detail from the original scene.

Bit Depth Explained

The number of colors used for quantization is related to the color depth or bit depth of the digital image.
A bit depth of n allows 2ⁿ different colors. Examples:
- A 2-bit digital image allows 2² (i.e., 4) colors in the image.
- An 8-bit digital image allows 2⁸ (i.e., 256) colors in the image.
The most common bit depth is 24. A 24-bit image allows 2²⁴ (i.e., 16,777,216) colors.

Basic Steps of Digital Image Retouching

Crop and straighten the image
Repair small imperfections
Adjust the overall contrast or tonal range of the image
Remove color casts
Fine-tune specific parts of the image
Sharpen the image

Parallels Between Digital Image and Digital Audio Editing

Tweening

To create movement and changes of visual content over time, without having to manually create the content frame by frame.
The computer interpolates the changes between 2 keyframes.

Possible Causes for Tweening Problems

Multiple symbol instances in the same keyframe
Classic tween applied to shapes
Shape tween applied to symbol instances
A mix of symbol instances and shapes in the same keyframe

Creating Animation with Motion Guide

Create keyframes like you would create a classic tween animation.
Create a motion guide layer for the tween animation:
- In the timeline, right-click (Windows) or Control-click (Mac OS) on the motion tween layer.
- Choose the option of motion guide.
In the motion guide layer, draw a path (using pencil or pen tool) in one single stroke. Do not create multiple strokes.
For each keyframe of the tween animation, drag the symbol instance to snap on the path.

Q- You can tween the position of a symbol or shape. Name three other properties of a symbol or shape that you can animate using tweening.

Answer: rotation, width, height, opacity (classic and shape tweens only), color (classic and shape tweens only)