Image Size
图像尺寸

Image size refers both to the height and width of the image in pixels and the file size. Large graphics take a long time to download over the Web and many people will become impatient. Try to keep your graphic files less than 35K in size.

图像尺寸涉及到图像的高度和宽度（单位：像素），以及生成的图像文件尺寸大小。从互联网下载大图会耗费很长时间，很多人会因此感到不耐烦。所以，尽量使你的图形文件小于35K。

Image resolution also affects the size of an image. The standard resolution for Web graphics is 72 dpi (dots per inch). Most image editing programs have commands to change the resolution. For example, in Adobe Photoshop choose Image Size from the Image menu to set the resolution.

图像解析度同样会影响图像的大小。网络图形的标准解析度为72dpi（dots per inch：每英寸点数[1英寸约2.54厘米]）。大多数图像编辑程序都包含改变解析度的指令。举个例子来说，在Adobe Photoshop中，可以选择图像菜单的设置解析度指令来改变图像尺寸。

Also make sure your graphic is not larger than 600 pixels wide. Images wider than that require scrolling on smaller monitors. Most graphics applications have commands that display the size of the image in pixels. For example, in Adobe PhotoShop choose Image Size from the Image menu to see the dimensions of an image.

尽可能保证你的图形宽度不要超过600像素。如果图像宽度超过这个宽度，那么，有些小型显示器就会要求使用滚动条来浏览整张图形。大多数图像应用程序都包含以像素来显示图像尺寸的指令。举个例子来说，在Adobe Photoshop中，可以选择“图像尺寸”中的“图像”菜单来查看一个图像的尺寸。

For example an image that is 720 pixels wide is too large to fit within a standard browser window. You would have to scroll horizontally to see the entire image (unless your video resolution is set very high) and horizontal scrolling is big taboo on the Web.

举个例子来说，一个图像的宽度是720像素，这相对于标准的浏览器窗口来说太大了一点，你将会使用水平滚动条来查看整个图像（除非你的视频解析度非常高）并且禁止在网络中使用水平滚动条。

Transparency
透明度

The GIF 89A file format enables designers to designate one color of a graphic to be transparent. If a transparent graphic appears on a colored or textured background you will be able to see the background through the transparent parts of the graphic.

GIF 89A文件格式可以使得设计师将图形中的一个颜色设置为透明。如果透明图形出现在有色背景或织纹背景上，你可以透过图形的透明部分看到整个背景。

The figure below illustrates the problem with non-transparent graphics. Notice that Figure 1 has the white background of the GIF appearing against the grey background of the table. Figure 2 is the same graphic except saved in GIF 89A format with grey as the transparent color. Notice that the background color of the table cells appears.

下面的图示阐明了非透明图形的问题。注意：图表1的Gif图片拥有一个白色背景，它与台面上的灰色背景形成对比；图示2中同样的图形并没有将GIF 89A格式设置为灰色透明色。注意：背景色是成区块式分布的。

图示 1  以GIF格式存储的白色背景图像

图示 2  这同样是GIF 89A格式，将已选的灰色作为透明色

图形简介：第一部分 图形简介：第三部分

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