Talking about Custom Filter in Photoshop 6.0
The custom filter is the most powerful filter in the entire filter family. Use it to create custom filters, such as filters that can create effects such as sharpening, blurring, and embossing. Custom filters are located in the other filter groups in the filter menu. It allows users to define their own filters, which is very flexible. Below, we will introduce the working principle and usage of the custom filter.
Custom filter principle
Select a custom filter from the Other submenu of the Filter menu. The dialog box is shown in the figure.
The dialog box has a set of option boxes arranged in a 5 × 5 matrix and two additional options of scale and offset. The value at the center of the option box indicates the program should increase the current pixel brightness value by multiples, and the value in the option box adjacent to the center box indicates the relative brightness relationship. Generally speaking, the grid in the center represents the target pixel, and the remaining grids represent the corresponding pixels around it. The number in the grid is the parameter value of each pixel, and the size of the parameter represents the influence of the hue of this pixel on the target appearance. Photoshop multiplies the brightness value of the center pixel by the value in the box to get the brightness value of the corresponding pixel. The setting range of the value in the option box is any integer between -999 ~ 999.
The value in the Scale box indicates the division value of the total value of the input brightness, and the parameter setting range is 1 ~ 9999. Offset adds the value of scaling displacement to the scaling calculation result as compensation, and the parameter setting range is -9999 ~ 9999. Therefore, through simple mathematical operations, it can be concluded that in theory there are about 2000 × 10000 × 2000 × 25 custom filters.
However, because the computer's gray level is 256, the type of custom filter is actually much smaller than this number, but it still shows strong power.
When the filter is working, Photoshop recalculates the brightness value of each pixel in the image or selected range, adds the brightness of the multiplied data in the dialog box matrix, then divides it by the scaling value, and then adds it to the displacement value. Get the brightness value of the pixel.
note:
1. If the multiplier of the brightness value of a pixel is too large, it will eventually become white, and such a filter is meaningless. Therefore, it is necessary to maintain a balanced relationship with the initial brightness value while creating the filter effect. To do this, you must ensure that the sum of all values ​​in the matrix is ​​1.
2. If the sum of all values ​​in the matrix is ​​greater than 1, increase the value of Scale so that the sum of all values ​​in the matrix divided by the value of Scale is 1. If the sum of all values ​​in the matrix is ​​not equal to 1, you can also use Offset to correct the value.
Principles for creating filters
The following principles must be followed when creating a filter:
1. Create a sharpening filter: you need to increase the contrast between adjacent pixels, and a series of negative values ​​should be used around the center frame. And ensure that the values ​​in the matrix are distributed symmetrically with the center of the matrix in the horizontal and vertical directions.
2. Create a blur filter: You need to reduce the contrast between adjacent pixels. A series of positive values ​​should be used around the center frame. It must also be ensured that the values ​​in the matrix are distributed symmetrically with the center of the matrix in the horizontal and vertical directions.
Through the above introduction, you can see the powerful functions of the custom filter, in this item you can create relief, blur and sharpening effects. The author will not give a detailed introduction here, and friends who are interested in this can practice it by themselves. Then click the "Save" button to store the custom filter. When you need to use it, click "Load" to call up the custom filter.
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