PS文件菜單中的另存為和另存為網頁格式的區(qū)別

Photoshop Save For Web
The Save For Web dialog box doesn't provide as much flexibility in the ouput image file formats as the Save As dialog, but it does offer more flexibility with each supported option. Supported output file formats include:
•       JPEG - Selection of Quality level (1-100). No transparency.
•       GIF - Different palette sizes (2-256) and dithering options define quality. Supports single-bit transparency.
•       PNG-8 - Reduced color depth (2-256 colors) and dithering options defines quality. Supports multi-bit transparency.
•       PNG-24 - "Lossless" 24-bit quality. Supports multi-bit transparency.
•       WBMP - Black & White dithered output.
（附圖見下面的中文版）
Main window for Save for Web
The focus on this page will be on the JPEG output format.

Photoshop另存為網頁格式
另存為網頁格式沒有像另存為那樣提供很多中保存圖像文件的格式選擇，但是它為每種支持的格式提供了更靈活的設置。支持的格式包括：
•       Jpeg－可以設置圖像保存質量（1－100％）。無透明度。
•       Gif－通過設置調色盤大?。?－256色）和顏色抖動來確定保存圖片的質量。支持單色透明度。
•       Png-8－通過設置調色盤大小（2－256色）和顏色抖動來確定保存圖片的質量。支持單色透明度。（原文中png-8透明度的說法貌似有誤？）
•       Png－24－無損24位質量。支持透明度。
•       Wbmp－黑白抖動輸出。  

另存為網頁格式的主窗口
按上圖中的設置將輸出jpeg格式文件。

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Save For Web JPEG output
Because the Save for Web command is intended to be used for images that are destined for display on the internet, one of the primary goals is in optimizing the file size as much as possible while still retaining acceptable image quality. To this end, two methods are used to achieve this: a) a live preview of changing JPEG compression quality sliders and b) the removal of all unnecessary metadata (JPEG markers) in the output file.
The main features in Save for Web include:
•       Optimize to File Size: Ability to automatically select both the file format (JPEG or GIF) and JPEG compression level to achieve the selected file size.
•       Removal of EXIF metadata. For many this is a useful feature, while others will completely avoid Save for Web because of it. For simple images on a web site or for privacy reasons, you may want to hide the time/date a photo was taken, or other parameters. But, if you plan to share your images on a photo hosting site and would like to indicate the focal length, aperture and other parameters to your viewers, Save for Web will not be the right method.
•       Removal of Optional Markers. In most output JPEG files, special markers are used to indicate additional information or provide resiliency in the case of errors / corruption. The Save for Web method will remove these and still allow JPEG decoders to work.

另存為網頁格式之jpeg輸出
保存為網頁格式目的是輸出展示在網頁上的圖片，保存的主要的目的之一是在維持圖片質量的同時盡可能地縮小文件體積。保存為網頁格式使用了兩種方法達到此目的：a) 在拖動滑動條更改jpeg質量設置時提供即時預覽；b）移除輸出文件中所有不必要的信息（jpeg標記）。
另存為網頁格式的主要特色有：
•       優(yōu)化文件大?。嚎梢宰詣舆x擇文件格式（jpeg或gif）和選擇jpeg的壓縮率，以實現(xiàn)選定的文件大小。
•       移除Exif信息。很多時候這是一個有用的功能，而另一些人則會因為此功能而不使用另存為網頁格式。對于簡單的網頁圖片來說，或者出于保護隱私，你也許希望隱藏照片拍攝的時間日期以及其它參數(shù)。但是，如果你想要在網絡相冊中分享你的照片，并且希望觀看者看到拍攝的焦距、光圈和其它參數(shù)，那么就不適合使用另存為網頁格式了。
•       移除可選的標記。在大多數(shù)jpeg文件中，有一些記錄附加信息、或是在出錯/崩潰時用以恢復的特殊標記。另存為網頁格式會在jpeg文件依然能被解碼的前提下移除這些標記。

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ICC Color Profiles
Both Save for Web and Save As give you the option of including the ICC Color Profile within the image. Color profiles are used to the viewer's display how the RGB values within the image data should map to real-world colors. Assuming you have a color-managed environment (calibrated and profiled monitor), this profile is used to display the colors as they were intended to be shown.
Unfortunately, most web browsers don't read this profile and most people don't have calibrated monitors, so the default color space, sRGB is generally assumed. Therefore, if you are sharing your photos on the web, and your photos were shot in a color space such as Adobe RGB, it is strongly advised that you convert to sRGB first. Once you've done that, there is little need to include the ICC profile within the file.
Comparison of JPEG Markers
The differences between the output of the two JPEG compressed file saving methods is easily visible when comparing the JPEG (JFIF) files themselves. The JPEG (JFIF) file format specifies a number of mandatory markers as well as some optional ones. The chart below shows how Photoshop CS2 Save as and Photoshop CS2 Save for the Web compare at a low level, with the help of JPEGsnoop:

ICC顏色配置：
另存為網頁格式和另存為都提供了是否嵌入ICC顏色配置的選項。顏色配置是用來讓圖片文件的RGB數(shù)值在用戶顯示器上顯示出更真實的色彩。假設你有一個經過顏色管理的環(huán)境（校準和配置過的顯示器）配置能讓顏色顯示更接近預期的效果。
很不幸的是，大部分瀏覽器不支持顏色配置，并且大部分人沒有校準過的顯示器，所以默認假設是sRGB色彩空間。因此，如果你在網上分享照片，如果你的照片拍攝時使用的是其它色彩空間，例如Adobe RGB，那么強烈建議你轉換為sRGB。如果你這樣做的話，就基本不需要在文件中嵌入ICC顏色配置了。
通過對比jpeg文件，兩種jpeg壓縮文件保存方式的區(qū)別是很容易識別的。jpeg（jfif）文件格式中列入了一些強制的標記和一些可選的標記。下面的表格是photoshop另存為和另存為網頁格式的輸出文件的對比。