第四次作业

1. 解释名词

1. ASCII: ASCII (/ˈæskiː/ (About this sound listen) ASS-kee),[1]:6 abbreviated from American Standard Code for Information Interchange, is a character encoding standard for electronic communication. ASCII codes represent text in computers, telecommunications equipment, and other devices. Most modern character-encoding schemes are based on ASCII, although they support many additional characters.
   ASCII is the traditional name for the encoding system; the Internet Assigned Numbers Authority (IANA) prefers the updated name US-ASCII, which clarifies that this system was developed in the US and based on the typographical symbols predominantly in use there.
2. Color(颜色) Color (American English) or colour (Commonwealth English) is the characteristic of human visual perception described through color categories, with names such as red, orange, yellow, green, blue, or purple. This perception of color derives from the stimulation of cone cells in the human eye by electromagnetic radiation in the visible spectrum. Color categories and physical specifications of color are associated with objects through the wavelength of the light that is reflected from them. This reflection is governed by the object’s physical properties such as light absorption, emission spectra, etc. 颜色或色彩是通过眼、脑和我们的生活经验所产生的一种对光的视觉效应。人对颜色的感觉不仅仅由光的物理性质所决定，还包含心理等许多因素，比如人类对颜色的感觉往往受到周围颜色的影响。有时人们也将物质产生不同颜色的物理特性直接称为颜色。

   2.简答

3. 写出字符“A”,“中”的 ASCII 码、Unicode 码、utf-8 编码。
   ASCII:0x41
   UNICODE: 0x0041
   UTF-8:0x41
4. 黄色(yellow)的RGB编码是( 255, 255, 0 )
5. 从网上下载一个 BMP 格式图像,用图片编辑工具另存在 jpg、 png、tiff 格式。问三种格式中,哪种格式显示质量好?相对于 BMP 格式,压缩率各是多少?
   答：tiff的显示质量最好，jpg,png,tiff的压缩率分别为14%，34%，77%。
6. Winrar压缩文件是lossless, or lossy 方法？
   lossless