Resolution is an important concept associated with the image, which is a technical parameter that measures image detail performance. However, there are many types of resolution, and the meaning is different. Correct understanding of the specific meaning of resolution in various situations, clarifying the interrelationship between different representations, is a crucial step. The following is a reference for several common image input / output resolution and different image input / output devices for your reference. Image resolution image: refers to the amount of information stored in the image. This resolution has a variety of measuring methods, typically measured at the pixel number (PPI) per inch. The image resolution and the value of the image size determines the size and output quality of the file. The more disk space occupied by the value, the larger the disk space occupied by the graphics file. The image resolution affects the size of the file with a proportional relationship, ie the file size is proportional to its image resolution. If the image size is maintained, the image resolution is doubled, and its file size is increased to four times. Scan resolution scan resolution: Refers to the resolution set before scanning an image, which will affect the quality and performance of the generated image file, which determines what image will be displayed or printed. If the scan image is used for screen display of 640 × 480 pixels, the scan resolution does not have to be greater than the device resolution of the general display screen, that is, no more than 120dpi. But in most cases, the scanning image is to output in a high resolution device. If the image scan resolution is too low, the effect of the output is very rough. Conversely, if the scanned resolution is too high, the information needed to exceed printing is generated in the digital image, which not only slows the printing speed, but also makes the subtle transition of the image hue when the printout is printed. Under normal circumstances, the image resolution should be twice that of the screen frequency, which is currently the standards used in most output centers and printing plants in China. In fact, the image resolution should be 1.5 times that of the screen, about this problem, I am afraid it will be controversial, and the specific image itself is indeed different, the situation is indeed different. To learn more, please see "Web Screen Angle and Output Resolution". Screen Resolution: Also known as the screen-screen frequency, refers to the number of points per inch of the screen used by the printing gray scale image or the score color image. This resolution is represented by the number of rows per inch (LPI). The bit resolution of the image of the image: also known as the depth, is the number of bits used to measure the storage information of each pixel. This resolution decision can be marked as the possibility of how many color levels. Generally, there are 8-bit, 16-bit, 24-bit or 32-bit color. Sometimes we also call the bit resolution as the color depth. The so-called "bit" is actually referred to as the number of "2", 8 digits is 2 eight times, that is, 8 2 multiplication, equal to 256. Therefore, an image of an 8-bit color depth that can be expressed is 256. Device Resolution: Also known as output resolution, refers to the number of points that can be generated on various output devices, such as displays, inkjet printers, laser printers, and plotters. This resolution is measured by DPI. At present, the device resolution of the PC display is between 60 and 120dpi. The resolution of the printing device is between 360 and 1440dpi. 1. Scanners, printers, displays for hardware devices such as scanners, printers, and displays, their resolution uses DPI (DOTS PER INCH). The resolution of the scanner is determined from three aspects: the optical part, the hardware part, and the software section. That is, the resolution of the scanner is equal to the resolution of its optical components, and its own resolution obtained by handling analysis by hardware and software.
The optical resolution is the actual number of optical components that the scanner can capture within each square inch area refers to the physical resolution of the scanner CCD, and the real resolution of the scanner, its value is made of CCD The pixel point is divided by the value obtained by the maximum sweep size of the scanner. A scanner having a resolution of 1200dpi, the resolution of its optical portion accounts for only 400 to 600dpi. The resolution of the expansion portion (generated by hardware and software) is analyzed by a computer, and the blank portion is scientifically fill (this process is also called interpolation). Optical scanning and output is one-on-one, what is the scan, and what is output. After the computer's hardware and software is handled, the output image will become more realistic, and the resolution will be higher. The scanners sold on the current market have the soft and hardware expansion function of the resolution. Some scanners are written on 9600 × 9600dpi, which is only the maximum resolution obtained by software, is not the real optical resolution of the scanner. Therefore, the scanner is speaking, its resolution has an optical resolution (or said optical resolution) and the maximum resolution. We say that a scanner has a resolution of up to 4800DPI (this 4800DPI is the sum of optical resolution and software difference processing), which means that when the scanner is input, on the 1 square inches of scanning web, can be collected 4800 × 4800 pixel points (Pixel). The image size generated after the resolution of 4800dpi is 4800 pixel × 4800 pixel. When the image is scanned, the higher the scan resolution, the more fine the resulting image, the larger the generated image file, but the interpolation component is also. We said that a resolution of a printer is 360dpi, which means that 360 color points that characterize the image output effect can be printed when using the printer to output an image. The larger the number of printer resolutions, indicating that the smaller the color point of the image output, the more fine the output image effect. The size of the printer color point is only related to the hardware process of the printer, and is independent of the resolution of the output image. We say that a resolution of a brand is 80dpi, which means that the display of the display can generate 80 light points on each inch screen within the valid display of the display. For example, a 14-inch display (the length of the fluorescent screen is 14 inches), the point distance is 0.28mm, then: Display resolution = 25.395mm / inch ÷ 0.28mm / dot≈90dpi (1 inch = 25.3995 mm). When the display is factory factory, the DPI value of the characterization resolution is generally not marked, only the spacing is given, and we can calculate the resolution of the display according to the above formula. Based on our calculated DPI value, we can further estimate the highest display mode supported by the display. It is assumed that the 14-inch display fluorescence screen valid display range is 11.5 inches, due to the horizontal direction of the display and 4: 3, so that the horizontal width of the valid display range is 4X inch, the vertical height is 3X Inch, according to mathematical ticking theorem, x = 11.5 ÷ 5 = 2.3 inches. Therefore, the effective display range width is 2.3 × 4 = 9.2 inches, the vertical height is 2.3 × 3 = 6.8 inches. The maximum display mode is approximately: 800 (9.2 × 90) × 600 (6.8 × 90), which is used to represent a pixel (Pixel) with a point (DOT). The above mainly described the device resolution of the scanner, printer, and display. Strictly speaking, the resolution of an image of the device resolution and the image of the device is the concept of both communication and distinction.
The device resolution is determined by the production process of the hardware device, although the resolution of some devices can be adjusted by software, but they have a limit of maximum resolution, and users cannot have any breakthroughs to it. The resolution of the image is a measure of the extent of the image itself. For scanners, printers processed images, their resolution is measured in PPI (Pixelsper Inch) in the number of pixels per inch. The image used for computer video processing, indicates the resolution in the level and vertical direction, such as 800 × 600, 640 × 480, and the like. Whether the image itself is fine and only related to the resolution of the image itself, but is independent of the resolution of the hardware device that handles its hardware device, but whether the processing result of the image is finely related to the resolution of the device that is dealt with. For example, an image of a 90PPI is fine, if it is printed on a printer that is 40dpi, the printing effect is quite bad. For the scanner, the high and low degree of resolution is proportional to the extent of the generated image, but its resolution can only give an initial value for the image resolution (this PPI value and the DPI of the resolution of the scanner) The value is equal) and does not limit the resolution of the image, and we can use software to adjust the resolution of the scan generated image. In addition, it should be noted that we generally say that an image of 640 × 480 is said to be the size of the image, which does not include the meaning of image resolution. 2. The number of resolution digital camera resolutions of digital cameras determines the size of the high quality picture that is finally printed, or the size of the screen can be displayed on the computer display. The digital camera resolution is high, depending on the CCD (Charge Coupled Device: charge coupled device) chip in the camera, the more pixels, the higher the resolution. From this, it can be seen that the distinction of digital cameras is also determined by its production process. When the factory is fixed, the user can only select digital cameras with different resolutions, but cannot adjust the resolution of a digital camera. In terms of similar digital cameras, the higher the resolution, the higher the camera grade, but the data file generated by high-resolution camera is large, the speed of processing, the speed, memory and hard disk of the processing, and the corresponding software are more High requirements. The size of the digital camera pixel level and the ultimately can print a certain resolution size, which can be simplified using the following method: If the resolution of the color printer is n DPI, the digital camera horizontal pixel is M, the maximum printable photo is M N inches. For example, the printer's resolution is 300dpi, and the image file of the digital camera of 3600 is not interpolated. The maximum picture size is 12 inches (3600 ÷ 300). Obviously, the larger the size of the digital photo to be printed, you need a higher pixel level digital camera. The method of calculating the display size is the same as the method of printing size. 3. There are two ways to represent the resolution of the projector's resolution projector, one is represented by a television line (TV line), and is additionally represented by pixels. Taking a television line indicating that its resolution is similar to a TV, which is mainly provided in order to match the television signal of the projection. In the pixel mode, it is generally represented as 1024 × 768 or the like. From a sense, this resolution is limited to the frequency and field frequency of the VGA signal of the input projector. When the frequency of VGA signals or field frequencies exceed this limit, the projector cannot be protected normally. Relationships of relationships related to frequency and frequency and resolution can refer to the relevant information, and details are not described here. 4. The resolution of commercial printing fields is in commercial printing, and the resolution is represented by the LPI (LINES Per inch) of the LPI (LINES PER INCH) in an equal distance per inch.
In the traditional commercial printing plate, the plate is added to the original image before the original image, which is composed of a network line equal to the transparent part of the opaque part. These network lines are also gratings, and their function is to cut the light anatomical image. Since the light has a diffraction physical characteristics, the light passes through the network cable, and the point to reflect the size of the original image image change, which is halftone. A halftone point does not exceed the area of a grid, the more the network cable, the more the image of the image, the better the image quality. Therefore, LPI represents resolution in the commercial printing industry. 5. The resolution of the TV is in the TV industry, and the resolution refers to the number of black and white stripes that can be distinguished in the fluorescent screen, which is a television line (TV line). The TV standards used in our country are PAL system, which specifies 25 frames per second, and 625 per frame. Due to the use of an interlaced method, the 625 row scan line is divided into odd rows and even lines, which constitutes a quicker of each frame, even two games, because the electron beam is scanned from above, so there is The electron beam returns from the end point back to the starting point, during which the blanked scan line is impossible to break down the image. The scanning counter period accounts for approximately 8% of the entire scan time, so the number of effective rows used to scan images in 625 lines are only 576 lines, thereby deriving the resolution of the image in the vertical direction of 576 points. According to the current 4: 3 aspect ratio TV standard, the resolution in the horizontal direction should be 576 × 4/3 = 768 points, which has obtained the common image size of 768 × 576. In addition, in computer video capture, we will also encounter a PAL type image size that follows CCIR601 standard with a size of 720 × 576. For NTSC formulations we have accessible, it specifies 30 frames per second, 525 rows per frame, and each frame is used, each frame consists of two fields, and its image size is 720 × 486.6. The resolution of the mouse resolution mouse refers to the number of points that can be detected per move, the higher the resolution, the higher the quality. Previously, the resolution of the mouse is usually 100dpi, and the current mouse resolution is from 200 dpi to 400dpi. High resolution mouse is usually used for drawing and accurate computer drawing, etc.. 7. The resolution of the resolution touch screen of the touch screen refers to the number of contacts that split the screen into recognizable contacts. The number of contacts in the horizontal and vertical directions is usually used, such as 32 × 32. Some people think that the higher the resolution of the touch screen, which is not the case, and should be considered according to the specific use when selecting the touch screen. The touch screen with analog technique is very high, and 1024 × 1024 can be reached, and it is possible to work with some similar screen paintings and writing (handwritten recognition). Under most occasions, the application of touch technology is just to make people touch "button" to select software design, and there is no need to use such high resolution. For example, when using a touch screen on a 14-inch display, the actual size of the display area is generally 25cm × 18.5cm, and a touch screen of a resolution is 32 × 32 can split the screen into 1024 0.78cm × 0.58cm (more than a cigarette. Small) contact. The person's finger pressing the touch screen of the touch screen is much more than the diameter of the cigarette, so such a contact is already enough. Point (DOT) and Pixel Difference DPI Pixels (Pixel) in the DPI (Pixel) in the image resolution is two concepts that are easily confused, and the point in the DPI can be said to be the smallest display unit of hardware devices. The pixels can be one point, but also a collection of multiple points.
When the scanner scans the image, each of the scanners corresponds to each pixel of the formed image, so the DPI value set when the scan is equal to the PPI value of the scanned image, at this time Can be marked. However, in many cases, the difference between the two is quite large. For example, an image having a resolution of 1 PPI, outputs on a 300DPI printer, at which time the image has a 300 × 300 points at the time of printing. There is also a similar problem in the application of the computer display, such as a 12-inch display area of about 200mm × 160mm, if the spot diameter of the fluorescent screen is 0.31mm, the maximum display of the maximum display on the fluorescent screen is 640 (200 ÷ 0.31) × 480 (160 ÷ 0.31), the corresponding resolution is 80dpi. This 80DPI is this: 640DOT ÷ (200mm ÷ 25.3995mm / inch) ≈80dot / incap or 480DOT ÷ (160mm ÷ 25.3995mm / inch) ≈80dot / inch. In this case, the display mode of the display card can be set to 640 × 480, and 1 Pixel consists of 1 DOT. If the display mode of the display card is adjusted to 320 × 200, when a 320 × 200 image is displayed, one pixel is corresponding to four spots.
The image resolution function indicates a variety of methods of image resolution, which mainly depends on different purposes. What to discuss below is the role of resolution in various situations, as well as their relationship between them. 1. The role of the resolution in the flat design is in planar design, the resolution of the image is measured in a PPI, and its and the image of the image determines the size and image quality of the image file together. For example, an image is 8 inches wide, 6 inches height, with a resolution of 100ppi. If the size of the image file is not changed, that is, the total number of pixels is unchanged, and the resolution is reduced to 50ppi, which is unchanged in the width ratio. In the case, the width of the image will become 16 inches, which will become 12 inches. These two figures before and after printing output change, we will find that the latter's field is 4 times the former, and the image quality has dropped a lot. So, what is the phenomenon of sending the two changes before and after the two changes? For example, send them to the display mode of 800 × 600 display, we will find that the picture size of the two figures, the picture quality is no different. For a computer's display system, the PPI value of an image is meaningless. It works that the total number of pixels included in this image, that is, another resolution representation of the previous example: horizontal direction The pixel number × the number of pixels in the vertical direction. This resolution representation also represents a wide high size at the time of image display. Two pictures before and after the PPI value thread, the total pixels are 800 × 600, so two images are the same in the same resolution, the same appear. Readers may try this example. 2. The image of the resolution in the print output is processed in the computer, sometimes output printing. In most printing methods, CMYK (Mine Red, Blue, Huang, Black) Four-color ink is used to express colorful colors, but the printing performance is colorful and TV, the photo is different, it uses a halftone point The processing method can express the continuous tone of the image, unlike the two, can directly exhibit changes in continuous tones. In order to facilitate understanding of the processing method of halftone, we are analyzed in black and white photos. Carefully observe the photos on the newspaper with a magnifying glass, which can be found that these photos are composed of black and white points, and because the size of the point is different, the photo exhibits a change in black and white adjustment. So, how is these different sizes? The answer to this problem can be found from the traditional printing process. Depending on the experience of the printing industry, all LPI values in printing have such a relationship with the PPI value of the original image, that is, the maximum size of the PI value = LPI value × 2 × printed image ÷ The maximum size of the original image. Generally speaking, only followed this form, the original image can be better reflected in printing. The LPI value used in the print is relatively fixed. Usually, the paper printing is 75LPI, and the color printing is 150LPI or 175LPI, so in the case of 1: 1 printing, the resolution of the original image should be 150 ppi, 300 ppi, and 350 ppi, respectively. In fact, we often use the desktop printer that uses the processing method of halftone points. The above formula is also applicable, but in the printing process, they do not use a physical screen, but by mathematical calculations to achieve halftone points. Treatment. A half-color adjustment point generated in these printers, with a number of print points, obviously constituting a halftone point print point, the greater the gradation range which can be expressed. For example, to simulate 256 grayscale changes, 16 × 16 = 256 print points constitute a halftone point. On the other hand, for the commonly used 360DPI printer, the row screen at this time is only 360/16 = 22.5 lines, which makes the line in the print image are very obvious, and the image quality is also affected.
