Introduce several ways to eliminate moiré at the image processing stage

Moire is a tainted, disturbing moire that results from data grid overlap conflicts. Moire is usually produced in three stages of image processing.

1. Scan for highly detailed textures: For example, when scanning an image on a textured fabric, moire occurs, which is caused by the scanner itself. The scanner is not sensitive enough to the details of the reading, and the resulting moire is present in the scanned image and can hardly be removed.

2. Incorrect screening angle output: When multi-color images are output at the wrong screening angle, moire will appear on the images printed on the printer. In addition, if the screen angle does not use the optimal value, it will inevitably appear moire.

3. Scanning pre-screened images: When scanning an image that has already been printed, the continuous tone information on the photo or transparencies cannot be scanned. Instead, it is a halftone dot. The scanner partially recognizes the space between the dots, but cannot copy it as it is or convert it to continuous tone. As a result, the image contains moire.

Based on the degree of damage to the overall image quality, several methods for eliminating moiré are introduced in order.

First, reduce the moire when scanning halftone images
When scanning black and white mesh tone images, the following steps usually eliminate the space between dots.

1. Scan the image at twice the normal resolution minus 10 pixels. For example, if a halftone image is typically scanned at a resolution of 300 dpi, it is now scanned at 590 dpi.

2. In Photoshop, select Filter\Blur\Gaussian Blur (Filter\Blur\Gaussian Blur). This filter has great damage to the image, so only lower values ​​should be used, and pixels with a radius of 0.7 to 1.2 should be sufficient.

3. Select Image\Image Size.

4. In the Image Size dialog box, select the "Constrain Proportions" and "Resample Image" options, you can change the resolution without affecting the width and height, and then set the interpolation to "Bicubic" (secondary cube).

5. Enter 300 in the Resolution field.

6. Click "OK" to halve the resolution and remove 3/4 of the image pixels. Usually this will also remove most of the pattern.

7. Evaluate the image. If the dot patterns are reduced enough, continue with other editing tasks. If not, proceed to the next step.

8. Evaluate the image again. If there are still a small amount of textures, apply Filter\Noise\Despeckle (filter\varicolor\speckle).

Source: China Packaging Network