2. Press Ctrl+Alt+I to view the picture size.
3. It can be seen that the size and width of this picture are 1920 pixels and the height is 1200 pixels.
Suppose we need to change the picture size to 400*400px. When we enter 400 in the width, you will find that the height will be 250, which obviously does not meet the required size. At this time, we can enter 400 in the height first, and then click OK.
5. Press ctrl+J to copy a layer, then press D to quickly change the front and background colors to black and white, and press Ctrl+Del to fill the background layer with white.
6. Press Ctrl+Alt+C to open the canvas size dialog box, then enter 400 in the width and click OK.
7. At this time, the picture size is 400*400 pixels (you can press ctrl+Alt+I to view the modified picture size), then adjust the position where the picture needs to be displayed according to your own needs (move the picture with the mobile tool), and then save the picture directly.