① BMP-BMP image file format
BMP is an image file format that has nothing to do with hardware equipment, and it is also a standard bitmap format that we often see on PC and Windows system, and it is widely used. It uses bitmap storage format and does not use any other compression except image depth, so BMP files take up a lot of space. Its biggest advantage is that it can be "accepted" by most software, which can be called a universal format.
BMP is a popular image format in the past. Now, when PC runs Window, BMP(Window bitmap) image is mainly used as wallpaper. BMP can provide lossless compression, and the compression method is RLE (Run-length Coding), which is an excellent choice when creating wallpaper image files. Sometimes, when looking for wallpaper pictures saved as RLE compressed files, there will be recognition errors in Window. Therefore, it is best to turn off RLE compression function before use.
② JPG-JPEG file format
JPEG is the abbreviation of Joint Photographic Expert Group, and the file is named ". Jpg "or" jpeg”。 JPEG format is one of the most widely used formats at present, and JPEG is also one of the two main file formats used for image processing in the World Wide Web (JPEG and GIF, the size of JPEG format files is generally smaller than GIF format files).
One advantage of JPEG format is that it can compress image data. JPEG is a lossy compression format, which can compress images in a small storage space. Repeated or unimportant data in images will be lost, so it is easy to damage image data. Especially, if the compression ratio is too high, the quality of the restored image after final decompression will obviously decrease. If you pursue high-quality images, you should not use too high compression ratio. The compression ratio of JPEG is usually between 10: 1 and 40: 1. The higher the compression ratio, the lower the mass. On the contrary, the smaller the compression ratio, the better the quality.
Therefore, JPEG image files are relatively small. The smaller the image files are, the more disk space will be saved, and the more time will be saved when downloading from the Internet.
③ JP2-JPEG 2000 file format
As an upgraded version of JPEG, JPEG2000 has a compression ratio about 30% higher than that of JPEG, and supports both lossy and lossless compression. An extremely important feature of JPEG2000 format is that it can realize progressive transmission, that is, the outline of the image is transmitted first, and then the data is transmitted step by step, so as to continuously improve the image quality and make the image display from hazy to clear. In addition, JPEG2000 also supports the so-called "region of interest" function, which can arbitrarily specify the compression quality of the region of interest on the image, or select the specified part to decompress first.
④ GIF-GIF file format
GIF (Graphic Interchange Format) originally means "Image Interchange Format", which is an image file format developed by CompuServe Company in 1987. The data of GIF file is a continuous tone lossless compression format based on LZW algorithm. Its compression ratio is generally around 50%, which does not belong to any application. At present, almost all related software supports it, and a large number of software in the public domain are using GIF image files. The data of GIF image file is compressed by variable length compression algorithm. Therefore, the image depth of GIF varies from lbit to 8bit, which means that GIF can support 256-color images at most. Another feature of GIF format is that images with multiple colors can be stored in a GIF file. If the data of multiple images stored in a file are read out one by one and displayed on the screen, the simplest animation can be formed.
GIFs are divided into static GIFs and animated GIFs, which support transparent background images and are suitable for various operating systems. "Body shape" is very small, and many small animations on the Internet are in GIF format. In fact, GIF is to save multiple pictures as a picture file to form an animation, so in the final analysis, GIF is still a picture file format.
⑤ tiff-tiff image file format.
Tiff (Tagged Information File Format) is a lossless 24-bit color image format, which can keep the color and lines of the original image, but it takes up a lot of space. TIFF is designed for cross-platform use, so it is accepted by most systems and image editing software.
The image file in TIFF format is very large. For example, a 2-megapixel image takes up almost 6MB of memory capacity, so TIFF is usually used for more professional purposes, such as book publishing and posters. , which is rarely used on the Internet.
⑥ png-png image file format
The full name of PNG is portable network graphics format. Is a very new file format, and PNG is the most undistorted format at present. It can compress images with indexed color of 256 or less, and also supports gamma correction. Even better, it is designed into a network format.
PNG format is different from GIF format and is not limited by 256 colors. Unlike JPEG format, it does not use lossy compression. The advantage of this format is that you can get high-quality images; The disadvantage is that your file is relatively large, which means it takes longer to download your pictures online.
⑦ EXIF-EXIF format
EXIF format is a digital camera image file format advocated by Fuji Company in 1994, which is actually the same as JPEG format. The difference is that it can also store exposure data such as shooting date, aperture, shutter and flash data, incidental information and small-size images.
8 WBMP-WBMP format
Wireless bitmap (WBMP) is a standard image format used by mobile computer devices. This format is specially used for WAP pages. WBMP supports 1 bit color, that is, WBMP images only contain black and white pixels, and cannot be made too large for correct display in wap phones.
Pet-name ruby ⑨MBM——MBM format
MBM format file is a bitmap file format of Symbian OS, which is a multi-bitmap file. Since an MBM file may contain multiple bitmaps, bmconv will also generate a bitmap header file MBG, which provides an ID for accessing bitmaps. When loading a bitmap from an MBM file, the corresponding header file should be included, and the appropriate identifier should be used as the parameter of the method of loading the bitmap.
At present, there are nine commonly used formats supported by mobile phones on the market. I'm sure you know exactly which format to choose. Here is the definition of standby screen. The clarity of a picture is not determined by its size KB, but by the following factors:
1, the clarity of the source of the picture itself;
2, the number of pictures;
3. Modify the magnification of the picture;
4. Whether the resolution of the picture matches the resolution supported by the mobile phone;
5. The matching degree between the color of the picture and the mobile phone;
6, the format of the picture