There are many file formats for image storage, but only a few are widely used as practical standards. For digital printing applications, there are three commonly used data formats: TIFF, EPS, and JPEG. The EPS and TIFF formats are the two basic formats that desktop publishers are most interested in; while the JPEG format affects those most of the time People working on multimedia; using other formats such as: PICT, GIF, BMP, WMF, etc., are usually converted into the above-mentioned three commonly used file formats before use.
TIFF file format
TIFF is an acronym for Tagged Image File Format. This file format was developed by Aldus and Microsoft for scanner and desktop computer publishing software and is used to store black and white images, grayscale images, and color images. The defined storage format has now become an important file format for publishing multimedia CD-ROMs. Although the history of the TIFF format is longer than other file formats, it is still the most widely used industry-standard bitmap file format. This is mainly due to the fact that the specifications of the TIFF format have been repeatedly improved. The TIFF bitmap can have any size of size and resolution. In theory it can have infinite depth, ie 1-8 bits, 24 bits, 32 bits (CMYK mode) or 48 bits (RGB mode) per sample point. The TIFF format can encode grayscale, J-health, CMYK mode, index color mode, or RGB mode. It can be saved in compressed and uncompressed formats. Almost all jobs that involve bitmaps can handle TIFF file formats—whether it's placing, printing, trimming, or editing bitmaps.
The TIFF specification allows the use of two color modes, CMYK and RGB, to divide an image into four overprint colors and save the image before color separation in TIFF format. Placing a TIFF format file in a page layout or similar program does not require further color separation. When the cyan printing plate is printed, the program simply pulls the cyan channel; when printing the red printing plate, it simply pulls the magenta channel; and so on. TIFF format can also save the index color bitmap, but few people do it. For indexed color images, the GIF format is more often used.
The TIFF format can contain both compressed and uncompressed pixel data. The compression method (LZW) is non-destructive (the data of the image is not reduced, ie, the information is not lost during processing), can produce a compression ratio of about 2:1, and the original document can be reduced to about half.
The current version of the TIFF format supports high-resolution color, which divides different parts of an image into blocks, or chunks of data. For each block, there is a flag that provides information about what the block looks like. The advantage of the block is that software packages that support the TIFF format only need to save the portion of the image that is currently displayed on the screen. Parts of the image that are not displayed on the screen are also stored on the hard disk and are not loaded into memory until they are needed. This feature is important when editing a very large high resolution image.
In TIFF files, no tools contain screen processing instructions. Screen processing is controlled by a program that prints TIFF format files. If you want to save the screen processing instructions while saving the bitmap, you must use the EPS file format. However, the TIFF format handles the clip path. Both QuarkXPress and PaceMaker can read the clip path and correctly subtract the background.
EPS file format
Encapsulated Postscript format. The Postscript language is a page description language designed by Adobe for printing files to any printer that supports the Postscript language. It is like Basjc, C, or any other programming language except that it is optimized for printing text and images on paper. When you work on a Postscript printer and tell the word processor (or any other application) to print a page, the computer writes a program describing the page in Postscript and sends the program to the printer. The printer actually contains a full-featured computer and a Postscript language interpreter to execute this program, drawing graphics on virtual paper in memory and printing it on paper.
An EPS file is a Postscript file that includes file header information. Using file header information, other applications can embed this file into a document. The EPS file has some restrictions, and these restrictions do not apply to standard Postscript files. These restrictions are mainly rules to ensure that EPS files can be inserted into different files without damaging the file. For example: In Microsoft Word, you can embed an ESP file in a Word document in a Word. The most popular application of EPS files is to embed them in desktop publishing files, especially those created by PageMaker or QuarkXPress. Desktop Color Separation (DCS) was developed by Quark and used for Process color processing. The DCS image is an EPS grid or image and consists of five parts: a low-resolution screen preview, plus cyan, magenta, yellow, and black layers. The DCS version 2.0 document may include more than 4 types of overprint colors, and may also include a certain number of spot colors or high fidelity color separations.
The EPS file format can be used for encoding pixel images, text, and vector graphics. If the EPS is only used for images like the Qin basis (for example, the Adobe Photoshop program is selected as the output), the hanging net information and the tone copy transfer curve can remain in the file, while TIFF does not allow such information to be included in the image file.
Since the EPS file is actually a collection of Postscript language code, it can be printed in a variety of ways on Postscript printers. Software that creates or edits EPS files can define capacity, resolution, fonts, and other formatting and printing information. This information is embedded in the EPS file and then read and processed by the printer. There are hundreds of printers that support the Postscript language, including all image typesetting systems used in the desktop publishing industry. Therefore, the EPS format is a file format used by the professional publishing and printing industry.
The EPS format is a format for printing. The Postscript language code embedded in the EPS file provides an important print definition, but this makes the file size larger. In addition, the value and memory overhead required to set up a Postscript engine in software is also high. As a result, most web browsers do not support EPS files, and most image viewing shareware and free software also do not support EPS files. For this reason, the EPS format cannot be used on the Web site's image display.
JPEG file format
The JPEG file format is known for its "Joint Photographic Experts Group" standard for experts who want extremely dark images. Now, it has risen to the main format of the zip file published by the print and the World Wide Web.
The images saved in the JPEG file format are actually a mixture of two different formats: the JPEG format specification itself, which defines the compression method for the image, and is included in the format of the image data for the resolution and color mode. Photoshop and other applications that can actually read and write JPEG file formats save image data in the JFIF file format (JPEG File Interchange Format) or other formats that are very similar to the JFIF format. The JFIF file format is just a simple way to compress an image grid or a surround JPEG without any more.
The original JFIF file format specification history allowed 8-bit grayscale images and 24-bit RGB images, but Adobe 'modified' this format to also handle 32-bit CMYK mode data, but most layout applications actually Can not be separated from the CMYK mode JPEG image, so Adobe does not make much sense of this modification. JPEG file format allows the use of variable compression method, save 8-bit, 24-bit, 32-bit depth image.For example, when When saving a Photoshop image in JPEG format, Photoshop offers several save options: low compression, medium compression, high compression, and best resolution, etc. Experiments have shown that when printing or viewing on a monitor At the time, JPEG can generally compress the image to one-tenth of the original size without noticeable difference.The image will be decomposed into small squares of 8×8 pixel image units.This JPEG distortion is sometimes found in news pictures. The picture was greatly compressed before being electronically transmitted and then printed at a high magnification.
JPEG uses a lossy compression format, which makes it an ideal format for quickly displaying images and saving better resolution. It is also because the JPEG format can greatly compress scanning or natural images, which facilitates storage or transmission via a modem, so it has been widely used on the Internet.
The JPEG format has a special variant called "Progressive JPEG". In creating the Progressive JPEG file elbow, the data is arranged such that when the image is loaded, only a blurred image is initially displayed, and as the data is loaded, the image gradually becomes clear.
The main disadvantage of the JPEG format is also its biggest advantage. That is, the lossy compression algorithm limits the JPEG to the display format, and loses some data each time the JPEG format image is saved. Therefore, it is usually only possible to save the image once in JPEG format at the final stage of creation.
If you want to print images, especially high-quality images, the TIFF format is a more appropriate choice.
Source: HC Printing Business Network