Bitchart document
The most commonly used image file format How to store the image Since I bought the first PC in fourteen years, I have been interested in the complicated information of the computer from 1 and 0. . The initial introduction I am noted is that when I am very flowing in the Magic Basic program list, they have a lot of data segments, you can use them and run to build their procedures. From this, I am clear whites no argument that it is more complex, but it is only a series of instructions for a series of elements of the computer micro-handlers. Connected, I am interested in the ASCII code, then the word processing file format, then come back, you will see the image. It is still a technique that is fascinated by the fans today. A bitmap stores the information you need to reproduce an image on an image. We often see images on the display, such as a beautiful sunset, but in the eye of the calculation, it is just a bunch of 0 and 1 combination. In the final analysis, it is the bit and bytes in the bitmap file to tell the computer what color is in this image, then the computer converts the color in the bitmap into the format compatible with its display card, Finally, output to the display. What is interesting in this process is how the computer explains the data in the bitmap, and the bitmap file has a variety of formats. Each format has its own method to coding pixel data encodes and gives some other information required for this format. Windows 95 can read the .bmp file and cannot read the .gif file, is because his designer makes the Paint program to decode the image data stored in .bmp format, not .gif. to here. You really want to know if there is a bitmap file in a bit. Is there a different type of format? Then let us simply look at the six bitmap file formats commonly used on the PC. Of course, there are other file formats, such as vector graphics, is to store some of the reproduction image instead of color data for each pixel, but the six bitmap file formats discussed here is the most likely you usually work. in use. BMP document BMP (Bitmap) file format is a bitmap file format of Windows, which is said that this format is used in Windows inner storage bitmaps. One. BMP format of document is often available. BMP's expansion name, but some is to expand the name, RLE is the run length encoding.
This kind of file means it uses the data compression method for. One of the two RE methods supported by the BMP format. BMP files can be encoded with color information per pixels 1, 4, 8, 16 or 24, which referred to as the color depth of the image, which determines the maximum number of color contained in the image. An image of a 1-BPP (bit per pixel, bit per pixel) can only have two colors. The image of a 24-bPP can have a colorless color than 16 megabytes. The next page describes the structure of a typical .BMP file. It is 8-BPP with 256 colors, and the file is divided into four main points: a bitmap file header, a bitmap message head, a color table and bitmap data. The bitmap file header contains information related to this file. If the bitmap data is started from which the bitmap data is started, the bitmap information includes information related to this image, such as the width and highness of the pixel. There is image color RGB value in the color table. For the display card, if it does not display more than 256 color, read and display. The program of BMP documents can be converted to the palette of the display card to produce the color. The bitmap data format of the BMP document relies on the number of bits used by each pixel color. For a 256-colored image, each pixel occupies one by section of the bitmap data part in the file. The value of the pixel is not RGB color value, but an index of the color table in the document. So in the color table if the first R / g / b value is 255/0/0, the pixel value is 0 indicates that it is bright red, and the pixel value is stored in the order from left to right, usually from the last line. begin. In a 256-color file, the first by section of the bitmap data is the color index of the image of the image of the lower left corner, the second is the color index of the pixel it right. If the number of bytes in the bitmap data is an odd number, it is necessary to add an additional byte in each row to adjust the integer multiple of 16 bits. It is not that the BMP document structure is listed in the table, such as 16 and 24-bpp, the file is not colored, the pixel value directs the RGB value, and the internal storage format of the private part of the other documents can also be varied.
For example, at 16 and 256 color. Bitchart data in the BMP file is compressed by the RLE algorithm. This algorithm uses the color of the color to replace the same sequence as the color, and Windows also supports OS / 2. .bmp file, although it uses a different bitmap information head and color table format. PCX file. PCX is the first image document format that is a bitmap file storage standard on a PC. It was the first Paintbrush software package in the Zsoft company, and in the 80-year early period, it was brought to the micro-soft and its product bundled, and the post turned into Microsoft Paintbrush and became a part of Windows. Although the use of this format is reduced, the file with. PCX expansion name is still ten minutes today. PCX file is divided into three parts, sequentially: PCX file header, bitmap data and an optional color table. The head length is 128 bytes, divided into several domains, including the size of the image and the number of encoded numbers for each pixel color. Bitmap data is compressed with a simple RLE algorithm. The last optional color table has 256 RGB values. The PCX format is originally designed for CGA and EGA. Later, it also supports VGA and true color display card, now PCX The image can be encoded with 1, 4, 8 or 24-bpp. TIFF file PCX format is the simplest in all bitmap file formats, and Tiffged Image File Format is the hardest type. TIFF files contain. TIF expansion name. It starts (IFH) with an image file header (IFH) of 8-by-segment, and the most important member in this document is a pointer to the data constructed as the image file directory (IFD). The IFD is a table called a mark (TAG) for distinguishing one or more variable length data blocks, and the mark contains information related to the image. TIFF file format defines more than 70 different types of tags, and some are used to store image widths and heights in pixels, and some are used to store color tables (if needed), of course, they must also be used to store bitmaps. The data is tagged, and a TIFF format file is determined for its markup, and this file structure is extremely easy to expand because you have to add some additional tags. Is it what is the TIFF document? One side, to write a soft piece that can be understood to be unacceptable to be used.
Multi-TIFF's reading program can only be identified, and the situation will be created in this case: a TIFF document created in a should be created, and the other should not be used. Creating a TIFF document can also add some markings that only have its own recognition, although Tiff's reading program can skip the markings that they don't recognize, but this is always a volume of the image. On the other hand, a TIFF file can contain multiple images, each of which has its own IFD and a series of columns. Bitchart data in TIFF files can be compressed by several ways, and a complete TIFF reading program should have RLE decompression shrinkage, LZW decompression zoom, and its algorithm decompression. However, it is worse that the decoding of LZW must have to get the same intention of the Unisys company, and it is often necessary to pay the duty. So that is, it is not possible to be a plurality of diabity TIFF reading programs that are incompetent when they encounter the image of the LZW algorithm. Although TIFF is the complexity, it is still a best cross-platform format. Because it is non-commonplace, it is not convicted or otherwise, it can encode any image to binary form and do not lose any property. GIF documents When a multi-image is the right to go to LZW, they will think of GIF (Graphics Interchange Format, reading JIFF) This is a common cross-platform bitmap file format, which is the initial COMPUSERVE company. GIF files are common with .GIF's expansion name, and large quantity on Compuseve. The symbol of GIF documents depends on which version it belongs to, and the two version of the present is GIF87A and GIF89A, the former is more simple. No argument, which is started with a 13-byte document header, and the file header includes a sign, version number, and other information of the GIF file. If this file has only one image, the file head is tight with a full list to define the color of the image. If there is a plurality of images (GIF and TIFF formats, it is allowed to encode multiple images in one file), and the full-color table is replaced by each image.
In the GIF87A file, the file header and the global color table are the image, which may be the first one in the head-tail phase, each image consisting of three parts, a 10-byte length Image description, an optional topical color table and bitmap data. For effective use space, bitmap data is compressed by the LZW algorithm. The GIF89A comin is similar to this, but it also includes an optional exhibition block to store additional information for each image. GIF89A details four expansion blocks: The image controls the expansion block, which is used to describe how the image is displayed (for example, it should be like a transparent to overwrite an image, or simply replace it); simple text Expansion block, it contains text displayed in the image; comment expansion block, which stores comments in ASCII text; Apply Extension block, which stores private data generated by the application. These extensions can be found in any place in the full-color table in the document. The most significant advantage of GIF is its wide use and its tightness. But it has two weaknesses, one is to use the GIF format to be placed up to 256 colors. Another can be more important, that is, the Software-making issuer who has used GIF formats must have to collect CompuservE, and each of them will pay a copy of the COMPUSERVE. This policy is made by the Compuserve imitation UNISYS, which inhibits the program to support GIF documents in his image application program. PNG file PNG (Portable Network Graphic, Yeading Ping) The file format is made as a replacement product for GIF, which can avoid the commonly encountered by GIF files. It reaches many features from GIF, and supports true color image. What is more important is that when it is compressed bitmap data, it uses a variety of variations of the LZ77 algorithm, and LZ77 is the former body of LZW, and can be used free of charge. From the limit of the article, it is not spending the PNG format in this way. JPEG file JPEG (Joint photographic excerts group, pronunciation JAY-PEG) file format is initially introduced by C-Cube Microsystems, to provide an effective way to store depth bit pixels, such as a photo scan, a lot of colors and fine ( Sometimes it is not fine).
