Detailed resolution (c)

Third, 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 dots when printed. Similar problems exist in the use of computer monitors. For example, the effective display area of ​​a 12-inch display is about 200mm×160mm. If the spot diameter of a fluorescent screen is 0.31mm, the maximum number of displayable spots on a fluorescent screen is 640 (200÷). 0.31) × 480 (160 ÷ 0.31), and the corresponding resolution is 80 DPI. This 80 DPI is this: 640Dot÷ (200mm÷25.3995mm/Inch)≈80Dot/Inch or 480Dot÷(160mm÷25.3995mm/Inch)≈80Dot/Inch. In this case, the display mode of the display card can be set to a maximum of 640×480. At this time, 1 Pixel consists of 1 dot. If the display mode of the display card is adjusted to 320×200, when displaying a 320×200 image, one pixel corresponds to four light spots.