22-3375 Web Design I // Columbia College Chicago

Using Images on the Web

QuizYou can use your notes.

Project 1: Group Crits

Is there a clear visual hierarcy?

Does the wireframe match the user goals (from last week)

Did the designer think through and represent the different user tasks (de!ned last week)?

Is the navigation clear; are the labels easily understood? Can the structure be further simpli!ed?

Does the designer present a clear vision for how this site will be an improvement over the current version — in visual design, content, and overall message?

Images can be integrated into your site as html <img> elements or pulled in

from your css.

How are images being used in the following sites?

Images on the Web

Images can be integrated into your site as html <img> elements or pulled in

from your css.

How are images being used in the following sites?

Rules for using web images

1 Save images in the right format

2 Save images at the right size

3 Measure images in pixels

What is the “right size”?

With the growing use of responsive design techniques and faster connections, it is becoming less crucial for designers to have their images perfectly sized to their box.

The basic guideline is to have (just) enough pixels for your images to look great, however you are using them.

Image Formats

Screen image formats

Print image formats

jpg

jpgs are for images, like photographs, that have a lot of colors and gradations. It uses “lossy” compression, meaning that you can reduce the size of the image by reducing the quality of the image detail.

colors transparency?

24-bit:millions no

What is image detail?

Image quality is detail; the quality of the original capture can be accessed by how much actual live detail was recorded, pixel-by-pixel. The more you compress your jpgs, the more of these pixel-by-pixel details you making the same (blowing out). The result of too much compression is jpg artifacts and posterization.

GIGO

Exercise

Use Save for Web to save out a jpg

png-24

There are two kinds of png images: 24-bit (png-24) and 8-bit (png-8). png-24 is a great format because it supports alpha transparency, which allows you to have images with transparent shadows, anti-aliasing, etc, and color underneath will show through.

There is no support for png-24 in ie6 (there is a workaround).

colors transparency?

24-bit:millions

yes(alpha transparency)

png-24: alpha transparency

png-8

png-8 is an 8-bit image format, meaning that it supports up to 256 colors. It supports binary transparency, meaning that pixels are either on or off – they have no transparency. This translates to jaggy edges (which you have to then plan for and work around).

You can reduce the color index (aka color table) to contain only the colors you need, resulting in very small image sizes. gif !les are saved in “index” color mode.

colors transparency?

8-bit:256 colors

yes(binary transparency)

Should I use png or jpg?

For photos, you almost always go with jpg, because pngs will usually be much larger.

For icons, backgrounds, tiles, etc, that need transparency, use png-24.

Exercise

Use Save for Web to save out a png 24

gif

gif if the workhorse for icons and vector graphics (like logos) that don’t need alpha transparency. Like png-8, it uses binary transparency. You can reduce the color index (aka color table) to contain only the colors you need, resulting in very small image sizes. gif !les are saved in “index” color mode.

colors transparency?

8-bit:256 colors

yes(binary transparency)

Exercise

Use Save for Web to save out a gif

Exercise

1 Fixed-width centered page

2 Fixed-height header with logo

3 Two Column layout, !oated

4 Absolute Positioning