How many types of image formats you have known?
Image format is the format of pictures stored in computer.
It uses a bit map storage format.
It doesnt use any other compression in addition to optional image depth.
So, BMP files take up much space.
BMP file image depth can be 1 bit, 4 bit, 8 bit and 24 bit.
Windows bitmap file format is compatible with other Microsoft Windows programs.
It doesnt support file compression and doesnt be applied to Web pages.
All in all, Windows bitmap file format has more disadvantages than advantages.
BMP file is suitable for the wallpaper in Windows.
Advantages
BMP supports the color depth from 1 to 24.
BMP format is widely compatible with existing Windows programs (especially older programs).
Disadvantage
BMP doesnt support compression.
This will result in files being very large.
PCX
PCX is short for Personal Computer Exchange.
There is a development process of this image file formation.
Later, Microsoft migrates it to Windows environment.
And it becomes a sub-function in Windows system.
It was first widely used in Windows 3.1.
PCX is the first file format that supports color images.
Now, it can support at most 256 colors.
PCX designer firstly introduced color image file format and makes it a very popular image file format.
PCX image file is made up of file header and actual image data.
Data of PCX image file are image data compressed with PCXREL technique.
PCX is an image file format for PC paintbrush.
Its image depth can be chosen from 1 bit, 4 bit or 8 bit.
Because it appeared in the early time, it doesnt support true color.
PCX file encodes with RLE.
Compressed image data are stored in file.
So, when collected data are written in PCX image file format, it will be encoded with REL.
When a PCX file is read, it will be decoded first and then displayed and processed.
<strong<Advantages
PCX is a standard format in many programs based on Windows and MS-DOS.
PCX supports internal compression.
DisadvantagePCX isnt supported by Web browsers.
TIFF
TIFF is short for Tag Image File Format.
It is a common image file format developed by Aldus and Microsoft Corporation.
TIFF is flexible and volatile.
TIFF is the most complex file format among existing image file formats.
It has the features of expansibility, convenience and changeability.
And it can be provided for image editing program running in IBMPC and other environments.
The first data structure in TIFF image file is called image file header (IFH).
This structure is the only part that has fixed position in TIFF file.
IFD image file directory is an information block with changeable byte length.
Tag, which is the core part of TIFF file, defines all image parameters in image file directory.
Every item in directory contains a parameter of image.
GIF
The full name of GIF is Graphics Interchange Format.
It is an image file format developed by CompuServe Company in 1987.
Data of GIF file is a lossless compression format based on LZW algorithm with continuous tone.
Its compression ratio is generally around 50%.
It doesnt belong to any utility.
Almost all software supports it.
There is a lot of software using GIF image file in public domain.
Data of GIF image file are compressed with variable-length compression algorithm.
The other feature of GIF format is that it supports storing several color images in one GIF file.
GIF decodes fast, because it uses interlaced GIF image.
It can be divided into four times of scanning when it decodes and displays.
This is the advantage of interlaced storage.
In addition, GIF doesnt support Alpha transparent channel.
JPEG
JPEG, short for Joint Photographic Expert Group, is the most common image format.
The filename extension is .jpg or .jpeg.
JPEG format, developed by Association of Software Professionals, is a loss compression format.
Image compression can be stored in small space, but the repeated or unimportant information will be lost.
In a word, its easy to damage image data by using this image format.
When you use high compression ratio, this will lower the quality of the decompressed image.
So, you had better not use high compression ratio if you pursue high quality image.
However, JPEG compression technology is very advanced.
It can remove redundant image data by using loss compression.
In other words, it can help us get better quality images with a minimum of disk space.
Whats more, JPEG, which can adjust image quality, is a flexible format.
It allows different compression ratio for file compression and supports many compression levels.
Its compression ratio is usually between 10 : 1 and 40 : 1.
The higher the compression ratio is, the lower the image quality will be.
Conversely, the lower the compression ration is, the higher the image quality will be.
For example, 1.37MB BMP file can be compressed to 20.3KB.
JPEG format compresses mainly high frequency information and remains better color information.
Therefore, it is suitable for Internet.
It reduces image transmission time and supports 24 bit true color.
It can also be used in image which needs continuous tone.
JPEG format is the most popular image format on the Internet.
Files can be compressed to the minimum size by using this image format.
Level 0 has the highest compression ratio, but its image quality is the lowest.
If you save image file in JPG format, the size of file is only 178 KB.
And its compression ratio is up to 24 : 1.
JPEG format is widely used, especially on the web andCD-ROMbooks.
JPEG 2000 is an updated version of JPEG.
Its compression ratio is about 30% higher than JPEG.
It supports loss and lossless compression.
And then it will transfer data, during the process, it will continuously improve image quality.
This makes image clearer and clearer.
In addition, JPEG 2000 also supports area of interest.
Compared with JPEG, JPEG 2000 has more advantages.
And it is compatible with later versions.
So, it can replace traditional JPEG format.
It can control the file size by using changeable compression ratio.
It supports interlace (for incremental JPEG files).
JPEG widely supports Internet standard.
Disadvantages
Loss compression will reduce the original data quality.
This kind of decline is cumulative.
File extension is
.tga.
It has been accepted by international graphic and image industry.
TGA has a simple structure belonging to a common format of graphic and image data.
It has a great influence on multimedia field and is a preferred form for computer-generated images to TV conversion.
Generally, both graphic file and image file shapes are square.
TGA format supports compression by using undistorted compression algorithm.
And its a good image format.
It is almost the same as JPEG format.
FPX
FPX is short for Kodak Flash Pix.
The extension name of this image file format is .fpx.
It was jointly developed by Kodak, Microsoft, HP and Live PictureInc and was published in June 1996.
This can reduce the load on the processor and memory to make it reduce image processing time.
Its storage way of multiple resolutions is accepted by many people.
It is an open standard vector graphics language and can arbitrarily enlarge graphic display.
Edge of image is very clear.
The text retains editable and searchable state in SVG image.
There is no limitation in font.
The size of generated fie is very small, so, it can be downloaded quickly.
This image format is quite suitable for designing high-resolution Web graphic pages.
PSD
Photoshop Document (PSD) is a specific file format of Photoshop image processing software.
File extension is .psd.
PSD format can support various image features like layers, channels, masks and different color modes.
Its an uncompressed original file saving format.
The scanner cant directly generate this kind of file format.
Sometimes, capacity of PSD files is very large.
CDR
CDR is a specific image file format of the famous graphics software, CoreIDRAW.
It has poor compatibility.
Other software systems can only read it.
This format uses YCC color mode to define colors in image.
YCC and CIE color space contains more colors than RGB color of monitor and CMYK color of print machine.
Most of the PhotoCD images have high quality.
It stores image by the way of ASCII.
UFO
UFO format is a specific image format of the famous image editing software, UIead PhotoImapct.
It can completely record all image attributes processed by PhotoImapct.
Whats more, UFO file records image information with objects rather than layers.
File name extension is .eps on PC platform while it is .epsf on Macintosh platform.
EPS format is mainly used to store vector graphics and raster images.
So, EPS format is usually used in printing and printout.
Several options of EPS format in Photoshop can achieve integrated control of printing and printout.
And in some cases, EPS format is better than TIFF format.
16.AI
AI is a kind of vector graphics file for ILLUSTRATOR output format of Adobe.
AI is also a hierarchical file which is the same as PSD file format.
Files stored in this format are easy to be modified.
This file format can be output with highest resolution as any size.
It has high compatibility and can be opened in CoreIDRAW.
CDR file format can be exported as AI format.
PNG
PNG (Portable internet Graphics) is the latest image file format accepted on Internet.
PNG can provide lossless compression image file length about 30% smaller than that of GIF.
It provides 24-bit and 48-bit true color image support and other technical support.
Because PNG is very new, not all programs can use it to store image files.
PNG supports high-level lossless compression.
PNG supports alpha channel transparency.
PNG supports gamma correction.
PNG is supported by the latest Web online window.
Older browsers and programs may not support PNG files.
As an Internet file format, PNG provides less compression compared with the loss compression of JPEG.
It is able to save the lighting information, but image may not be panorama.
Dynamic Range refers to the relative ration of the brightest and darkest parts in a scene.
HDRI has greater brightness ranges than normal RGB format (only 8-bit brightness range).
The maximum brightness value of standard RGB (red, green and blue) image is 255/255/255.
RAW
RAW means raw material or the stuff isnt processed.
Users can use some pieces of certain software on PC to handle RAW format image.
Storage and Advantages
We should know that in traditional sensors, each pixel only obtains one color.
Data carried in each pixel are usually 10 bit or 12 bit (12 bit is most common).
And these data can be stored in RAW file.
JPEG reduces file size by compressing original photo file, but this kind of compression will reduce image quality.
So, RAW is a compromise plan of the above two image formats.
It not only ensures image quality and color, but also saves storage space (compared with TIFF).
Some high-level digital cameras can output almost lossless compression RAW files.
Applicability
Some image processing software can handle RAW files outputted by cameras.
These pieces of software provide sharpness, white balance and color adjustment for RAW format photos.
These details cant be found in each JPEG or TIFF image with 8-bit channel.
When users handle RAW format images, they must use specific software offered by manufacturers.
This brings lots of inconvenience for image processing.
In addition, compared with JPEG image and TIFF image, opening and handling RAW file cost more time.
This solves compatibility problem and Adobe Photoshop CS is an example.
However, Adobe Photoshop CS doesnt provide comprehensive RAW processing prefs like the specific software offered by manufactures.
Poor compatibility is still the biggest limit in RAW format development.
