How to check the scan quality of the image?

Today, color flatbed scanners have been widely used in color desktop publishing systems and professional advertising design industries, home users are more because of the improvement of life products, but also have a strong demand for the purchase of these products, all kinds of The facts have played a positive role in promoting color image processing, but how can we get truly high-quality scanned images? In the previous article, we introduced to you that the factors that affect the quality of image scanning are caused by many aspects: resolution setting, color correction, image enhancement, file format, file storage, and system resources all involved in it. Even if all of the above problems are solved, it does not necessarily mean that you can sit back and relax. To get a perfect scan image, you need to check the quality of the scanned image. Most users are often neglected. Lose this point.

Check the quality of the scanned image, often need to start with the following aspects, image gradation range, image color and image brightness.

Check image tone range

For many novice users, checking image quality often means checking the tone of the image, thinking that good color is equivalent to a good image. In fact, this is just one aspect of the problem. The most critical factor in looking at an image is to check its gradation range, which is the level of the image. The so-called level is the degree of change from dark to light shades in the image. Checking the image level requires the use of professional tools, such as some professional graphics and image processing software Photoshop, ImagePais 2. These software's pipette tools can check the image level, especially for high light areas and dark areas.

If the highlights and shadows appear with large numbers of white or black of the same value, or the magnitude of the value change is very small, it means that the image level is poor. Using the "Level function" in Photoshop, you can also check the quality of the image from the color distribution map. If there are a large number of dark pixels on the left, it indicates that the whole image is dark; if there are a large number of bright pixels on the right, it indicates that The entire image is bright; if the scanned image is in good quality, the image is clearly structured and the color distribution map is even. In addition, Photoshop's "Histogram function" can also help users check the status of the scanned image to see if the continuous level transitions smoothly from light to dark, or if there is a band gap, if there is a clear band gap, the user The selected scanner density is low and should be adjusted accordingly.

Check image color

When the image has enough levels, check whether the color of the image is balanced, that is, whether the image has color cast or not. The easiest way to check the color balance is to check neutral gray. Gray balance is the gradual change from the smallest black (0%) to the largest white (100%) in the image, and is one of the important parameters for converting from RGB to CMYK. In theory, mixing equal amounts of C, M, and Y inks will produce neutral ash, but in fact, due to the difference in ink quality, it will cause a certain percentage of deviations, only a specific proportion. In order to achieve neutral gray. The user can determine the correct CMYK value from the Printing Inks Setup function in Photoshop.

The easiest way to check the color is to open the Info panel in Photoshop and move the cursor to the brightest highlight and darkest tone in the image. Note the data displayed in the Info panel, if the highlight and low-key areas are read. The RGB value is between 250 and 5, which means that the tonal range of the scanned image has enough detail and the image quality is very good.

In addition, the impression color of the image should also be checked to see if the colors of the sky, grass, and flowers are harmonious and uniform. However, most of them need human judgment and lack of science. Because the judgment of color is a complex visual and psychological process, and each person's aesthetic point of view and personality are different, they will have a particular preference for certain colors. Therefore, this method can only be used as a reference method for checking colors.

Check the brightness of the image

It is also very important to check the brightness of the image. By comparing it with the original, it is impossible to obtain the ideal image if the scanned image is too dark or too bright, too dark or too bright. Brightening an image that is too dark, adjusting the gamma value is definitely a convenient method, but doing so can cause the scanned image to lose information. In fact, the easiest way to check the brightness of an image is to compare it with an original and try to read the color value on the scanned image in CYMK mode to see if it is close to the original.

In fact, the scanning process has always been simple, but to obtain high-quality scanned images, there are too many variables involved. According to the experience of using scanners for many years, I think that if you want to get a perfect scanned image, the quality control of the scanned image is very important. Seriously doing the above points is an important factor in obtaining perfect output.

Reprinted from: Suzhou Computer Repair Network