Image File Types and How to Export Files from Photoshop
GIF Image Format
- Limited to 256 colors
- Supports transparency
- Supports animation (animated gif)
- "Lossless" compression - but if original has more than 256 colors, going to 256 colors or less loses information
- Compression algorithm takes advantage of areas of constant color
JPG Image Format
- Can have over 17 million colors (256 possibilities in red x 256 possibilities in green x 256 possibilities in blue)
- No transparency, no animation
- Better format for photographs than gif because most photographs have lots of colors
- Compression algorithm is lossy (one loses information) so if one is making a series of changes in a jpg, best to make all changes before saving rather than saving as one goes along
Quality and File Size for GIF and JPG
- Tradeoff between quality and image file size within each format
- jpg - quality setting between 1 and 100 (100 is largest file size, and best quality)
- gif - number of colors (256, 128, 64, 32, 16, 8, 4, 2)
- Can have over 17 million colors, just like JPG (24 bit)
- Supports transparency
- lossless compression
- Developed over patent concern about GIF
Bitmap and Vector Graphics
- GIF, PNG, and PNG are bitmap formats
- Vector graphics represent shapes in a mathematical way whereas bitmaps (also known as raster graphics) represent the color of each individual pixel
- Vector graphics can be blown up without loss of quality whereas enlarging a bitmap can lead to a pixelated look
Exporting from Photoshop CC
File > Export > Quick Export as ...
This is partially based on the first part of the Adobe video - https://helpx.adobe.com/photoshop/how-to/export-image-web.html
File > Export > Quick Export as PNG. PNG is the default.
However you can change the default by File > Export >Export Preferences where you can set the default format for the Quick Export to be PNG, JPG, GIF, or SVG.
For PNG, you can choose among three possibilities
- Transparency is checked - results in 32 bit image
- Nothing is checked - results in 24 bit image
- Smaller file (8 bit) - this limits you to 256 colors, the same as the limitation for a GIF
For JPG, you can set the quality (a number between 0 and 100, with 100 being the best quality and the largest file size)
You can also set the Quick Export Location, whether Copyright and Contact Information will be included, and whether to convert to the sRGB color space.
The Quick Export can be accomplished either by choosing File > Export >Quick Export or by right clicking on the layer that contains the image and choosing the Quick Export option.
An alternative to File > Export >Quick Export as ... is to use File > Export > Save for Web (Legacy). This alternative will eventually go away but is still present in Photoshop CC 2019 and Photoshop CC 2020.
Revised: November 18, 2019. Comments to William Pegram, firstname.lastname@example.org