Image processing apparatus, X-ray diagnostic apparatus, and image processing method

According to one embodiment, an image processing apparatus includes processing circuitry. The processing circuitry obtains a parameter value representing temporal information on blood flow for each pixel of multiple image data items, and generates a parameter image by determining a pixel value of each pixel according to the parameter value representing the temporal information on blood flow. The processing circuitry further generates a composite image of an X-ray fluoroscopic image of an object obtained in real time and a road map image using at least a part of the parameter image, and causes a display to display the composite image.