1. An image processing apparatus capable of generating a composite image by combining plural images at least including a foreground image and a background image, the image processing apparatus comprising: at least one controller including a processor configured to execute a program stored in a memory or a circuit configured to implement a function, the at least one controller being configured to: generate, in a case where the foreground image includes a plurality transparent pixels and a plurality of semi-transparent pixels and an arrangement state of the transparent pixels is a first arrangement state in the foreground image, the composite image by performing alpha blending to combine a semi-transparent pixel in the foreground image with a pixel in the background image and also performing alpha blending to combine a transparent pixel in the foreground image with a pixel in the background image; and generate, in a case where the foreground image includes a plurality of transparent pixels and a plurality of semi-transparent pixels and the arrangement state of the transparent pixels is a second arrangement state in the foreground image, the second arrangement state being different from the first arrangement state, the composite image by performing alpha blending to combine a semi-transparent pixel in the foreground image with a pixel in the background image and not performing alpha blending to combine a transparent pixel in the foreground image with a pixel in the background image.