Command Tips To use the filter you just used again, select Filter » Last Filter [Ctrl+F] from the menu; use the new option to use the newly used filter and remember to add an Alt key (Ctrl+Alt+F or Alt + Filter » Last Filter ).
Tip: To retire the last used filter or adjust the effect (or change the compositing mode), press Ctrl+Shift+F (Filter » Fade Filter... ).
If you recently copied a picture to the clipboard, Photoshop will use the size of the picture in the clipboard as the default size for the new image when creating a new file [Ctrl+N] ( File » New... ). To skip this feature and use the last setting, hold down the Alt key [Ctrl+Alt+N] (Alt + File »New...) when you open it.
Press Ctrl+Alt+Z and Ctrl+Shift+Z to go backwards and forwards in history, respectively (or you can use the menu in the history panel 
Use these commands). Use these hot keys in conjunction with the Restore [Ctrl+Z] (Edit » Undo) command to freely switch between history and current state.
Alt+Backspace and Ctrl+Backspace key combinations fill the foreground and background colors, respectively, and another very useful hotkey is Shift+Backspace - opens the Fill dialog box.
Tip: Press Alt+Shift+Backspace and Ctrl+Shift+Backspace to fill only the existing pixels (keeping the transparent area) when filling the foreground and background colors.
When holding down the Alt key (Ctrl+Alt+T or Alt + Edit » Free Transform) when using the free transform tool [Ctrl+T] (Edit » Free Transform ), you can copy the original layer (in the current selection) Transform on the copy layer.
Tip: Ctrl + Shift + T (Edit » Transform » Again) to perform the last conversion again, Ctrl + Alt + Shift + T (Alt + Edit » Transform » Again) to perform the transformation after copying the original.
To prevent the use of the crop tool [C] (Crop Tool) when the marquee snaps to the picture border, hold down the Ctrl key while dragging the control point on the marquee tool selection box.
To correct a tilted image, first use the measurement tool [U] to draw a line (like the border of the image, the frame, the horizontal lines between the eyes, etc.) on the map where the horizontal or vertical orientation can be referenced, and then select Image from the menu » Rotate Canvas » Arbitrary, after opening, you will find that the correct rotation angle has been filled in automatically. Just press OK to confirm.
Note: You can also use the cutting tool to complete the rotation and cutting in one step: first draw a box with the cutting tool [C], drag the control point on the selection box to adjust the angle and size of the selection box, and finally press Enter to rotate and cut.
Tip: The angle measured by the measurement tool is also automatically filled in the Digit Transform Tool (Edt » Transform » Numeric) dialog box.
Use the "Layer » New » Layer Via Copy" or "Cut Layer New (Ctrl+J)" command to complete in one step Copy & paste and cut & paste work.
Note: By copying (cutting) new layer commands, they are still placed in their original places, but they are pasted (cut) & pasted to the center of the picture (or selection).
Cropping the image (using the cropping tool or selecting Edit » Crop) loses all pixels outside the cropping range. To cut without loss, use the "Image » Canvas Size" command instead. Although Photoshop will warn you that you will perform some cuts, but for some reason in fact does not - all "cut out" of data are kept outside the screen.
Tip: ImageReady's cut command (Image » Crop) asks if you want to delete the clipping area or hide it.
Note: This has no effect on the index color mode (using the canvas size command in index mode will lose pixels outside the screen).
Hold down the Alt key [Ctrl+Alt+Shift+E] (Alt + Layer » Merge Visible) to merge all visible layers and merge them into the current layer.
Tip: You can also hold down the Alt key while merging layers (Layer » Merge Down ). This will copy the current layer and merge it into the previous layer. There is no corresponding hotkey for this command - Ctrl+Alt+E does not work.