An image display apparatus comprising: a display; a processor; a memory comprising a first buffer and a second buffer; and at least one program stored in the memory and executed by the processor, wherein the at least one program comprises instructions which when executed by the processor cause the image display apparatus to: obtain a planar-format image by decoding a video content, the planar-format image being a 360° planar-format image and represented by a first color space, perform graphics processing on the planar format image (10, 410) to obtain a sphere-format image corresponding to the planar-format image, the sphere-format image represented by a second color space, select a partial sphere-format image among the sphere-format image based on a user input on the sphere-format image, perform graphic processing on the partial sphere-format image to obtain a partial planar-format image, change a color space of the partial planar-format image from the second color space to the first color space, for performing image quality processing on the partial planar-format image; store the partial planar-format image of which the color space is changed from the second color space to the first color space in the first buffer, the first buffer being for storing a video image, generate an on screen display, OSD, image, store the OSD image in the second buffer, the second buffer being for storing a graphic image, perform the image quality processing on the partial planar-format image of which the color space is changed from the second color space to the first color space and which is stored in the first buffer, and control the display to display the image-quality-processed partial planar-format image with the OSD image. a display; a processor; a memory comprising a first buffer and a second buffer; and at least one program stored in the memory and executed by the processor, wherein the at least one program comprises instructions which when executed by the processor cause the image display apparatus to: obtain a planar-format image by decoding a video content, the planar-format image being a 360° planar-format image and represented by a first color space, perform graphics processing on the planar format image (10, 410) to obtain a sphere-format image corresponding to the planar-format image, the sphere-format image represented by a second color space, select a partial sphere-format image among the sphere-format image based on a user input on the sphere-format image, perform graphic processing on the partial sphere-format image to obtain a partial planar-format image, change a color space of the partial planar-format image from the second color space to the first color space, for performing image quality processing on the partial planar-format image; store the partial planar-format image of which the color space is changed from the second color space to the first color space in the first buffer, the first buffer being for storing a video image, generate an on screen display, OSD, image, store the OSD image in the second buffer, the second buffer being for storing a graphic image, perform the image quality processing on the partial planar-format image of which the color space is changed from the second color space to the first color space and which is stored in the first buffer, and control the display to display the image-quality-processed partial planar-format image with the OSD image. obtain a planar-format image by decoding a video content, the planar-format image being a 360° planar-format image and represented by a first color space, perform graphics processing on the planar format image (10, 410) to obtain a sphere-format image corresponding to the planar-format image, the sphere-format image represented by a second color space, select a partial sphere-format image among the sphere-format image based on a user input on the sphere-format image, perform graphic processing on the partial sphere-format image to obtain a partial planar-format image, change a color space of the partial planar-format image from the second color space to the first color space, for performing image quality processing on the partial planar-format image; store the partial planar-format image of which the color space is changed from the second color space to the first color space in the first buffer, the first buffer being for storing a video image, generate an on screen display, OSD, image, store the OSD image in the second buffer, the second buffer being for storing a graphic image, perform the image quality processing on the partial planar-format image of which the color space is changed from the second color space to the first color space and which is stored in the first buffer, and control the display to display the image-quality-processed partial planar-format image with the OSD image.