Lecture 4 - Graphics Continued Flashcards
How can you have a smaller file size, keep the quality and download the image quickly?
Optimize the image (reduce download time)
What are three image Optimization Techniques?
- File Formats: choose .jpg or .gif
- Compression: compress the image data
- Color Resolution
What file formats are appropriate for the web?
.jpg
.png
.gif
What is .gif max color scheme?
ie How many bits?
Max 8 bit color scheme therefore 256 colors
Good for clipart but not good for photos
.gif properties
Best for large areas of solid flat color
Tiny file sizes in comparison to .jpg
Allows for animation and a plug in is not required
What is a .jpg max color scheme?
24 bits so 16 million colors
.jpg properties
Good for photos, best for blends of color and softer shadow effects
Not good for well defined lines
Larger file size in comparison to .gif
What is compression?
To reduce the redundancy of the image data in order to be able to store or transmit/download data in an efficient form
Compress as much as you can without sacrificing quality
What are the two compression techniques?
- Lossless
2. Lossy
What is Lossless?
By compressing the original bits and bytes into less bits and bytes without losing any of the original information about the image
What is Lossy?
When compression occurs, some of the original information is lost.
Cannot get the information back once it is discarded
What compression algorithm does a .gif use?
Lossless
No data is discarded during compression, quality is kept
What compression technique is used for a .jpg?
Lossy
Data is discarded each time file is compressed, quality degrades
What are two uncompressed file formats?
- bmp
2. raw
What are three common compressed algorithms?
- .jpg
- .gif
- .png
How many bits is one byte?
8 bits
What does the ASCII Code state?
That each letter represents 8 bits which in turn is 1 byte
When looking at images, what is the human eye is more sensitive to?
Brightness
Color Resolution =
Bit depth
Does color resolution only apply to .gif files?
YES
How long does it take for an 8 bit color resolution image to download?
2 seconds
Dithering Technique
Lowers download time
Applies when converting .jpg to .gif
Instead of using true color, it uses 256 colors or less
Most common way of reducing colors and the final image is saved as a .gif
What is Dithering?
Juxtaposing pixels of two colors to create the illusion that a third color is present
How many colours does a browser safe palette have?
216 colours
