montage:tldr:07a5a

This command is using the "montage" tool to create a new image by combining multiple input images. Here's a breakdown of each part of the command:

1. ${image1-png}: This is a placeholder for the path or filename of the first input image, which should be in PNG format.
2. ${image2-jpg}: This is a placeholder for the path or filename of the second input image, which should be in JPG format.
3. ${imageN-png}: This is a placeholder for the path or filename of the Nth input image, which should be in PNG format. This indicates that you can specify multiple images by repeating this placeholder with appropriate names/numbers (e.g., ${image3-png}, ${image4-png}, etc.).
4. -geometry +0+0: This sets the geometry or placement of the input images. Here, it specifies that the images should be positioned at (0,0) coordinates.
5. -resize 640x480^: This resizes the input images. The "^" symbol ensures that the aspect ratio is preserved. The largest possible dimensions that fit within a 640x480 box will be used.
6. -gravity center: This sets the gravity or position where the images will be cropped in case they have off-sized dimensions. Here, "center" means the images will be cropped from the center.
7. -crop 640x480+0+0: This specifies the final dimensions of the output image after cropping. The dimensions are set to 640x480, and the crop starts at (0,0) coordinates.
8. montage.jpg: This is the filename/path of the output image that will be generated.

In summary, the command takes the provided input images, positions them at (0,0), resizes them while preserving aspect ratio, crops them to 640x480 dimensions from the center, and saves the resulting montage as "montage.jpg".