The best effect of displaying the original: resolution analysis of prepress equipment (below)

Mouse resolution

The resolution of the mouse refers to the number of points that can be detected per one inch of movement. The higher the resolution, the higher the quality. Previous mouse resolutions were typically 100 DPI, and current mouse resolutions ranged from 200 DPI to 400 DPI. High-resolution mouse is usually used for graphics and precise computer graphics.

Touch screen resolution

The resolution of the touch screen refers to dividing the screen into recognizable number of contacts. It is usually represented by the number of contacts in the horizontal and vertical directions, such as 32×32. Some people think that the higher the resolution of the touch screen is, the better. In fact, this is not the case. When selecting the touch screen, it should be considered according to the specific purpose. The touch screen with analog technology has a high resolution and can reach 1024×1024, which can be used for some similar screen painting and writing (handwriting recognition) work. In most cases, the application of touch technology is just to let people touch the "button" of the software design by hand, there is no need to use such a high resolution. For example, when a touch screen is used on a 14 inch display, the actual size of the display area is generally 25×18.5 cm, and a 32×32 touch screen can divide the screen into 1024 0.78×0.58 cm (smaller than a cigarette). The contacts. The contact of the human finger with the touch screen is much larger than the diameter of the cigarette, so such a contact is sufficient.

The difference between Dot and Pixel

Dots in the DPI and pixels in the image resolution are two concepts that are easily confused. The dots in the DPI can be said to be the smallest display unit of the hardware device, and the pixels can be either one point or more. Collection of dots. When the scanner scans the image, each sample point of the scanner corresponds to each pixel of the formed image. Therefore, the DPI value set during scanning is equal to the PPI value of the scanned image. One can draw an equal sign.

But in many cases, the difference between the two is considerable. For example, an image with a resolution of 1 PPI is output on a 300 DPI printer. At this time, each pixel of the image corresponds to 300×300 Dot when printing. Similar problems exist in the use of computer monitors. For example, the effective display area of ​​a 12-inch display is approximately 200×160 mm. If the spot diameter of a fluorescent screen is 0.31 mm, the maximum number of displayable spots on a fluorescent screen is 640 (200÷0.31). ) × 480 (160 ÷ 0.31), the corresponding resolution is 80 DPI.

The role of resolution

There are many ways to represent the resolution of an image, depending on the application. What will be discussed below is the role of resolution in various situations and their relationship to each other.

The role of resolution in graphic design

In the graphic design, the resolution of the image is measured by PPI, which determines the size and image quality of the image file together with the width and height of the image. For example, an image that is 8 inches wide by 6 inches high and has a resolution of IOOPPI. If you keep the size of the image file constant, that is, the total number of pixels does not change, the resolution is reduced to 50 PPI, and the aspect ratio remains unchanged. The width of the image will change to l6inch, and the height will change to 12inch.

The two figures before and after the printout change, we will find the latter's format is four times the former, and the image quality has dropped a lot. So, what happens when the figures before and after these two changes are sent to a computer monitor? For example, when they are sent to a display with a display mode of 800×600, we will find that the picture size of the two pictures is the same and the picture quality is not different. For a computer's display system, the PPI value of an image is meaningless. The function is the total number of pixels contained in the image, which is another resolution representation method mentioned earlier: Horizontal direction The number of pixels x the number of pixels in the vertical direction. This resolution representation method also shows the width and height of the image when it is displayed. The two figures before and after the change in the PPI value described above have a total number of pixels of 800,600. Therefore, the two images with the same resolution and the same format are displayed.

The effect of resolution at print output

Images processed in computers sometimes print out. In most printing methods, CMYK (magenta, cyan, yellow, and black) four-color inks are used to express rich and colorful colors, but the way in which colors are printed is not the same as that of photographs. It uses a half-tone dot processing. The method to represent the continuous tone changes of the image, unlike the latter can directly show the continuous tone changes. According to the experience of the printing industry, all the LPI values ​​on the printing have a relationship with the PPI value of the original image, that is, the PPI value = the LPI value × 2 × the maximum size of the print image and the maximum size of the original image.

In general, only by following this formula, the original image can be better reflected in the printing. The LPI value used in printing is relatively fixed, usually 75LPI for newspaper printing and 150LPI or 175LPI for color prints. Therefore, in the case of 1:1 printing, the resolution of the original image should be 150PPI, 300PPI, and 350PPI, respectively, for different purposes.

In fact, most commonly used desktop printers also use halftone dot processing methods. The above formula is also applicable, but they do not use a physical screen during the printing process, but rely on mathematical calculations to achieve halftone dots. Processing. A halftone dot produced in these printers consists of a number of printed dots. The more printed dots that make up a halftone dot, the greater the range of grayscale that it can represent. For example, to simulate 256 grayscale changes, 16×16=256 print dots are required to form a halftone dot.

Source: Greater China Graphic Arts Network

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