First, several concepts related to the resolution
To accurately grasp and understand the meaning of resolution, it is necessary to figure out the following concepts. Resolution: including device resolution, screen resolution, graphical resolution, scan resolution, and bit resolution. Device Resolution: Also known as output resolution refers to the number of points generated on various output devices, such as displays, inkjet printers, laser printers, hot wax printers, plotters. This resolution is measured by the amount of DPI, in general, the device resolution of the PC display is between 60 and 120dpi. The resolution of the printing device is between 180 and 720DPI. Screen Resolution: Also known as the web screen frequency, refers to the number of points per inch on the screen used by printing the gray level graphics or the different color. This resolution is calibrated by the number of rows per inch (RPI). Image resolution: Refers to the amount of information stored in the graph. This resolution has a variety of measuring methods, typically measured at the pixel number (PPI) per inch. The value of graphical resolution and graphics size determines the size and output quality of the file, the more disk space occupied by the value, the larger the graphics file. The graphical resolution affects the size of the file with a proportional relationship, ie the file size is proportional to its graphical resolution. If the graphic size is maintained, the graphical resolution is doubled, and the size of its file is increased to four times. Graphical resolution also affects the display size of the graphic on the screen. If the graphic resolution increases from 72 ppi from 72 ppi to 144 ppi (keep the graphic size unchanged) on a display of 72DPI, the graphic will be displayed on the screen with the actual size of the original graphic. Scan resolution: Refers to the resolution determined before scanning a graphic, which will affect the quality and performance of the generated graphic file, which determines what the graph will display or print. If the scanning graph 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 graphic is prepared for the output in the high resolution device. If the graphics scan resolution is too low, the graphics processing software may create some halftone points with the color value of a single pixel, which causes the output to be rough. Conversely, if the scanned resolution is too high, the information you need to exceed the print is generated in the digital graphics, which is not only slowed down, but also makes the subtle transition of the graphic tone when the printout is printed. In general, the correct scan resolution should be calculated using the screen resolution, scanning, and output graphic size of the printout. Multiply the maximum size of the output graph multiplied by the screen resolution, then multiplied by the network line number (generally 2: 1) to obtain the total number of pixels required. The total number of pixels is divided by the maximum size of the scan pattern, that is, the graphic scan resolution = (output graphic maximum size × net screen resolution × network line number ratio) / scan pattern maximum size. Bit Resolution: Also known as the number of bits used to measure the storage information of each pixel. This resolution determines how many colors can be displayed on the screen, which is generally 8 bits, 24-bit or 32-bit colors. Sometimes we also call the bit resolution as the color depth. Second, several image input / output devices resolution scanner, printer, fax machine, display, digital camera, projector, television, business printing and other input / output devices, and mouse, touch screen, etc. The meaning of clarifying its meaning, facilitating us to buy and use these equipment. The reader must pay attention to the resolution mentioned herein refers to the device resolution.
1. The resolution of the scanner, printer, fax machine, and displays is for hardware devices such as scanners, printers, fax machines, and displays that have a DPI (DOTS PER INCH) that can be generated per inch. The resolution of the scanner is determined from three aspects: the optical part, the hardware part, and the software section. That is to say, the resolution of the scanner is equal to the resolution of its optical components plus itself to process the resolution obtained 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 only written only 9600 × 9600dpi, which is only the maximum resolution obtained by the software interpolation, 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 greater the generated image file. 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, the smaller the color point characterizing the image output effect, the more fine the output image effect. For the size fixed image, the larger the printer resolution, the smaller the image size printed. 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. The fax machine is scanned (before sending) and printing (after receiving) function, see the relevant part of the scanner and printer resolution meanings when understanding its resolution. We said that a resolution of a brand is 80dpi, which means that the display of the display can generate 80 light points on each inch pattern 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 device resolution of the scanner, printer, fax machine, and display is mainly described above. 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 large resolution of a large limit, and users cannot have any breakthroughs to it. When describing and understanding the device resolution, we must use the resolution of the image it processed. The resolution of the image is a measure of the extent of the image itself. For scanners, printers, fax machine processing, the resolution is measured in the pixel 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, its 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 value of the DPI of the scanner resolution are Equal), does not limit the resolution of the image, we can use software to adjust the resolution of the scanned image (as shown in Figure 1). 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. Third, Point (DOT) and Pixel Difference DPI Pixels (Pixel) in the DPI (Pixel) in image resolution is two concepts that are easily confused, and the point in the DPI can be said to be the smallest display of hardware devices. Unit, and 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. 4. The role of image resolution indicates a variety of methods of image resolution, which depends primarily 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, namely: PPI value = LPI value × 2 × maximum size of the original image is 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. To this end, most printers use 8 × 8 halftone patterns, and the corresponding row screen is 45LPI. By formula, it can be calculated. For these printers, the resolution of the print image should be 90ppi. 3. The role of resolution in the TV industry is divided into horizontal resolution and vertical resolution in the TV industry. In most cases, both are equal, and therefore generally give only horizontal resolutions in technical indicators, whose measure Unit TV lines are often referred to as lines. As can be seen from the previous definition, this resolution is based on the human eye, so it depends on a large number of experimental statistics. According to the current TV standards in our country, the aspect ratio is 4: 3, and the number of scans is 625. Remove the scanning counter period, the effective scanning line is 576 lines, and the corresponding effective pixel is 768 × 576 (720 × 576), and therefore 768 × 576 (720 × 576) is also a standard for the television image and digital image mutual conversion. However, the resolution at this time can also be said to be the limit resolution of the television system, which is 625 × 0.7 = 438 lines. It can also be seen that the number of black and white stripes in the number of effective pixels and the resolution is not a correspondence of 1: 1. There are many factors affecting the resolution, typically estimate the size of the resolution in the bandwidth × 80 line / MHz of the brightness signal in the television device.
