Image-processing apparatus, method for controlling thereof, and computer program

An image-processing apparatus is provided. The apparatus includes a determining unit determining a type of image data; a holding unit holding color value for the still images, and holding a ratio for the moving image for each moving image, an updating unit updating the color value and the ratio, and a display unit displaying composite image data. For each piece of image data to be drawn, the updating unit updates each ratio based on a transmittance of the image data, updates the color value and a transmittance of a still image when it is a still image, and updates the color value data based on a transmittance of a moving image, and causes the transmittance to be further held as a ratio of the moving image when it is a moving image. The display unit displays the composite image data using the color value and the ratio.