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Establish the correct scanning concept
For image scanning, many operators have wrong understandings, lack of physical and chemical concepts and standardized methods for restoring and scanning color separations. They simply lead post-processing, that is, relying on screen colors for subjective arbitrary adjustments, resulting in high-end professional scanners and high-end electronic The advanced technology and powerful functions of networking have not been brought into full play.
In fact, scanning an image is not a simple matter. It requires reasonable settings for the scanner's resolution, tone, color, and other parameters. If the settings are not correct, the scanner may cause a large amount of image detail loss, color cast, and unclear black and white fields during the scanning process. Even if it is processed by various image software in the later stage, it will only further aggravate the loss of the image, and cannot obtain the effect similar to the original. Therefore, before scanning, we must establish the correct scanning concept, clarify the basic process of image scanning, set the scanning parameters correctly, and scan high-quality images.
Image scanning is technical and artistic. It is necessary to set and adjust the parameters of gray balance, tone contrast, color correction and sharpness from the technical aspects according to different types of manuscripts, but also from the aesthetic aspect of art. The relationship between color tone, saturation, spatial distance, light and dark, and luster changes. The level of the operator in these two aspects greatly affects the image quality. Therefore, to improve the image quality of current color prints, we must make up our mind to grasp the key technology of scanning color separation and train higher-level operators.
Selected scanned original
The quality of the scanned original directly affects the quality of the scanned image. At the same time when selecting the original: see if there are scratches or dirt on the surface of the original, whether the text and lines are complete, and whether there are missing pens or broken strokes. Second, see if the picture is color cast. Under natural light or a standard light source close to daylight color, observe whether the achromatic parts such as white, gray, and black on the reflective manuscript interfere with other colors, that is, whether the reflective manuscript screen has a color cast. Three to see whether the main colors are accurate. Generally speaking, the colors of reflective drafts (such as photos) are slightly more exaggerated than the colors of actual scenes, that is, they are more vivid than the original colors. For reflection drafts with characters as the main body, the facial skin color should be rosy as the standard. Four to see whether the contrast is moderate. The contrast of the reflection draft includes brightness difference, color contrast and contrast balance. Moderate brightness difference, there is a rich transitional color level between the high-key part and the dark-tone part; moderate color contrast, the reflection color density is large, and has a strong three-dimensional sense; the contrast is well-balanced, the same color is in the high-key part and The color performance of the dark areas is consistent.
Adjust the monitor correctly
Many designers have had such troubles: when the color image is processed by the computer, after output or printing, it cannot obtain the same effect as the display. Therefore, before performing image scanning, the display brightness, display color and other parameters of the display should be adjusted. It is best to keep these parameters consistent with the parameters to be set by the scanner or slightly higher, so that the screen display effect is basically consistent with the actual printed matter .
Place the original in the optimal scanning area
Place the original in the best scanning area of ​​the scanner to get the best image effect. This optimal scanning area was obtained after many tests: set all the controls of the scanner to automatic or default state, select all areas, and scan a blank, white or opaque sample with low resolution: open this in Photoshop The scanned image of the sample is processed using the image → adjustment → tone equalization command, and you can see where there are cracks, streaks, and black spots on the scanner. Print this file and cut out the best area (that is, the most stable area) to help us place the original.
Place the scanned object correctly
When processing scanned images, it is sometimes necessary to obtain images with a slant effect. Many designers often use professional imaging software to rotate the image. In fact, this not only wastes time, but also reduces the quality of the image to varying degrees. The correct approach is: how to rotate the page on which the image is designed, use a protractor to measure the exact angle of the original rotation, and then scan to get the highest quality image.
Choose the right scan type
Choosing the right scan type not only helps to improve the scanner's recognition success rate, but also generates files of appropriate size. Generally, the scanner provides users with three scanning types: color, grayscale and black and white. Before scanning, the appropriate scanning type should be selected according to the scanning object and the end use. The "color" scan type is suitable for scanning color photos. It requires multi-level sampling and storage of the red, green, and blue channels. This method generates large files; the "grayscale" scan type is often used for existing pictures. There are also mixed images of text and text, and the file size is moderate; the "black and white" scanning type is commonly used for scanning black and white originals. When using this type of scanning, the scanner uses 1 bit to represent both black and white pixels. The generated file is the smallest.
Now there is a color image, and the final result requires a grayscale image. So, whether to scan directly in grayscale, or first scan in color and then convert to grayscale? The author's suggestion is that it is best to use color scanning. Choosing color scanning can make various adjustments to the scanned originals. At the same time, the color information of color scanning is large, and the colors obtained after scanning will be more saturated and richer in layers. Then use Photoshop software to convert the color image into a grayscale image, the layer will be better. Conversely, if grayscale scanning is directly selected, the color of the image before scanning is lost, and there is little room for adjustment. The grayscale image layer after scanning is obviously not rich in color scan and then converted into grayscale image layers.
Choose the right scan resolution
Scanners usually provide a resolution range that can be set. In theory, the higher the resolution, the more pixels per inch of the scanned image, and the richer the original image details it expresses. The resolution setting of the scanner should be determined according to the end use of the scanned image. Since the highest resolution of the scanner is obtained by interpolation, scanning with an accuracy exceeding the optical resolution of the scanner will not only significantly improve the output effect, but will increase the storage of files and reduce the overall work for no reason. effectiveness.
In general, if you scan some engineering drawings or images that contain text information, you should set the scanning resolution as high as possible, so that the lines or text in the image will be more improved when the scanning resolution is improved. Close to the original appearance, each line stroke can also be distinguished relatively well; if the scanned image is only used to display the web page image, the scanning resolution can be set to 72dpi, so the generated image file is relatively small, which is beneficial to the image transmission on the Internet; if the image In the end, to print and publish, at least 300dpi resolution is required.
It is best to pre-scan
Many operators skip the pre-scanning step to save scanning time when scanning large-sized photos or documents. In fact, before the formal scan, the pre-scan function is very necessary, it is the first level to ensure the scanning effect. The pre-scan has two advantages: one is that the area to be scanned can be directly determined by the pre-scanned image, and the image is cropped and rotated to reduce the image processing process after the scan; the second is by observing the pre-scan After the image, you can roughly see the color and effect of the image. If you are not satisfied, you can set and adjust the scanning parameters again, and then scan again.
Adjust other parameters related to the image
In order to scan images with good effect and high quality, not only do all the above-mentioned settings work, but also all the scan parameters related to the image must be set as much as possible, such as the color balance parameters of the scanned image By adjusting, you can change the overall tone effect of the scanned image, and adjust the image scanning effect to a more ideal state.
Finally, it should be noted that, when a satisfactory scanned image is obtained after scanning, it is best to sharpen the image. Due to the limitations of the light-receiving components (such as CCD optical quality, etc.) and the quantization error caused by digital sampling, the scanned image is often not as clear as the original. Therefore, in image processing, it is important to improve the clarity of the scanned image through artificial processing, such as the application of Unsharp, Shapren, Sharpen More effects.
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