Storage and transmission of images

First, the storage, transmission and processing of image data

Image data can be stored in external memory, display memory or computer memory medium 3 medium, different storage media for different purposes. The image is stored in the display memory to show that the displayed image intelligence is viewed in the boot state, and disappears after the shutdown is called a soft copy. To facilitate fast access to image refreshes, the data in the display memory cannot be compressed. Therefore, the data in the display memory is "primitive original", real. Most image processing algorithms deal with such a set of data, the process of such data is usually not related to the programming environment. Image data in the form of files stored in the external memory as a permanent preservation, in order to save storage space, sometimes the image data needs to be compressed and then stored, compressed image data used to be decompressed. The image data needs to be stored in the computer's memory for processing, and the data can only be modified when it is processed in memory. Image data can also be transmitted over a computer network. Several types of image transfer are listed below: 1. Transmission between external memory and display memory     uncompressed and non-processed images can be transmitted directly between the external memory and the display memory, which is the fastest speed. 2. External memory and display memory transmit through memory compressed and need to process the image data can no longer external memory and display memory directly between the transmission, must pass through memory to transmit. 3. The transfer between memory and display memory     image processing data is often transmitted between memory and display memory. The handler reads the raw data from the display memory and sends the processing results back to the display memory for display. 4. External memory and memory transfer between     external memory and memory transfer between the less, mainly for data processing, such as file format conversion.     the first two kinds of transmission for image display and display image storage, commonly used in the second mode of transmission. The latter two are used for image processing, which is commonly used in the 3rd mode of transmission. 5. Transfer     image data between computers can also be transmitted between computers over a network or other communication line, in order to save costs, the transmitted data is usually compressed. Second, the storage structure of pixel data     Usually, the pixel data in the display memory and the external memory are all in one-dimensional structure positioning. Therefore, the image data that is not to be locked is similar to that stored in the external memory and display memory, and is also sequentially arranged by scanning, and the calculation formula of the pixel data stored in the external memory is the same as the formula in the display memory. In most cases, the formula for the number of bytes per line of uncompressed images is                           bytes per line = Bytes per pixel * Number of pixels per line     Image data in memory, can be used as a one-dimensional array, can also be represented by a two-dimensional array, the data type may be single-byte, short integer (two bytes) or floating point number, depending on the specific needs. Image processing also often access to the image data of a rectangular window, an image window of the pixel data into a one-dimensional array, its addressing method is the same as the display memory address, the original line width used to replace the window width. For structural consistency and easy routing of data, a one-dimensional single-byte array is recommended for processing.     if a two-dimensional array is used, the two dimensions of the array should correspond to the rows and columns of the screen, respectively. You should pay particular attention to their order when you use them, and you should ensure that the order in memory of the pixel data in the two-dimensional array corresponds to the order of storage in the display memory. In C language Program and Pascal language program is c[y][x], p[y][x]. where x is the column number and Y is the line number.     array defines the array whose elements are stored continuously in memory, so the array cannot be opened very large. In DOS environment, large-area image is generally used in dynamic memory application to establish a two-dimensional array, it is in the same row is continuous storage, but the adjacent two rows is not necessarily continuous. In a Windows environment, you can request a larger memory space without the above restrictions.

Storage and transport of images