Getting started with photoshop learning: selection and processing

Photoshop is a bitmap processing tool (other bells and whistles are ignored) -

Bitmap refers to a picture composed of several pixels.
Processing involves two things: selecting the target and changing the target.

Basic model of photoshop project:

1. Divide a bitmap into k layers and process them separately
2. Each layer is divided into m*n Pixel
3. Each pixel has 3 primary colors. Each primary color has 255 light points that can be bright or dark. The brightness and darkness are represented by numbers from 0-255

So, image processing is actually Control (256 * 3) * (m * n) * k light points.

How to choose which light points to control?

1. Use layer to select in k layer
2. Use selection to select in m*n matrix
3. Use color channel to select among 3 colors
4. Use a mask to select a selection in a layer and control it
5. Use the alpha channel to save the selection for later use

How to process the selected light points?
For pixels, you can adjust its hue, saturation, brightness or red, blue, green; for color points, you can only adjust its brightness (actually it is the number size, ranging from 0-255).

Under Image-Adjustment menu:
1. Levels: Control brightness. You can do fine processing on the bright and dark parts. This is actually selecting based on the brightness and then processing.
2. Curve: control brightness. You can do fine processing according to the different degrees of light and dark. This is actually to accurately select the brightness and then process it.
3. Hue/Saturation: Control hue, saturation, and brightness. You can select according to the color channel and then process it.
4. Channel Mixer: Actually, select the color channel and then adjust its red, blue, and green. Can be used to generate monochrome images.
5. Photo filter: Actually select all the light points, and then adjust their red, blue, and green. (Selecting a color has the effect of specifying red, green and blue colors)
6. Shadow/Highlight: It actually makes a comprehensive selection (shadow or highlight), and then adjusts its brightness (brightens the shadow and darkens the highlight).
7. Threshold: The actual selection is based on brightness (divided into those greater than the threshold and those less than the threshold). If it is greater, set it to white, and if it is less, set it to black.

Under the layer menu, process the layer:
1. Layer-Layer Style, perform external processing on the layer. (Consider the layer as a whole to add effects)
2. Layer - Create a new adjustment layer and perform internal processing on the layer. (Same as the method under Image-Adjustment, but it is processed for layers and does not destroy the original image)
3. Layer-New Fill Layer to quickly create a new layer with simple content.
4. Layer stacking types. The most commonly used ones are multiplication and filter color, that is, subtractive color and additive color.
1) Multiply: If the brightness of the lower layer exceeds that of the upper layer, the brightness of the upper layer will be used.
2) Color filter: If the brightness of the lower layer is not as good as the upper layer, the brightness of the upper layer will be used.
3) Other combination methods need to be further understood. It is roughly divided into four groups: subtractive color, additive color, dimming, and color toning.
5. Layer-Create Clipping Mask: Put the content of the upper layer into the shape of the lower layer

About the strategy (a series of actions that are more complex and can be used multiple times, save it and repeat it Use):
1. Under the filter menu, perform combination processing with a certain purpose, similar to applying a certain strategy.
(to be added, temporarily recorded: the elimination point is used to process perspective supplement, and the surface blur is used to process character skin)
2. Layer styles can also be regarded as strategic combinations, which can be saved or imported
3. Actions are used to record batch processing or perform batch processing

Basic tools:

1. Selection tools: used to select a selection, polygonal lasso tool, magic wand tool Most useful, combined with Select-Adjust Edges for fine selection. But it’s better to use a mask, which can record and select areas.
2. Processing tools: The brush is the most useful, and the others can be used flexibly. The bunch of buttons for spot repair are very useful when processing photos. These tools provide convenient and intuitive processing. (To be supplemented by learning)

TODO:
Look at the operation examples to deepen the understanding of each function, especially the use of the following two items:
1. Version
2. Adjustment layer

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