The resolution of WPS’s projector is 1920×1200. This does not mean that your images must be this exact resolution, but that your images should be resized to fit within those dimensions. You must decide which way to scale your image, some software (e.g. Lightroom) can handle this decision for you, but there’s a very simple set of “ABC” rules to decide how to scale your image:
A. If your image is longer in the vertical direction (portrait format), then set the height dimension to the projector’s vertical dimension of 1200
B. If your image is longer in the horizontal direction (landscape format) then set the width dimension to the projector’s horizontal dimension of 1920. Now check your image, and if the resized image has a vertical (height) dimension exceeding 1200 pixels, go back, and instead use the procedure from
C. If your image is equidistant (square format) then follow the procedure from step A.
Adding a black background to reach 1920×1200 is not necessary, the projection software will do this automatically. You can optionally add a border to your image, but this must still be within the bounds of the dimensions. Some images benefit from a border, some don’t.
Each photo editing program has a different way of changing the image resolution and other related parameters. The methods used by four common packages are described under Processing Software.