A video image processing method applied to a terminal, comprising: displaying an acquired video image on a screen; detecting operation points of a user on the screen, and converting screen coordinates of the operation points into target canvas coordinates on a target canvas; drawing a graph on the target canvas according to the target canvas coordinates of the operation points; and superposing the target canvas drawn with the graph on the video image, characterized in that the video image superposed with the target canvas drawn with the graph is fully displayed on the screen, and the user clicking a start of a graffiti mode triggers an initialization of the target canvas and a requesting of a memory space in a memory for the target canvas, wherein a size of the requested memory space in the memory for the target canvas is determined according to a preset size of the target canvas and an amount of memory per pixel, wherein the preset size of the target canvas is a resolution size of the target canvas, wherein under the condition that the memory space requested for the target canvas in the memory is fixed, the virtual canvas is used as an intermediate state for converting the screen coordinates of the operation points into the target canvas coordinates on the target canvas, which comprises: determining a virtual canvas according to facial features in the video image, a size of the virtual canvas being in a preset proportional relationship with a size of a face area in the video image in which the virtual canvas is square and the width of the virtual canvas is twice the distance between the eyes of a face in the face area in the video image; mapping the screen coordinates of the operation points onto the virtual canvas to obtain virtual canvas coordinates of the operation points; and mapping the virtual canvas coordinates of the operation points onto the target canvas to obtain the target canvas coordinates of the operation points on the target canvas. displaying an acquired video image on a screen; detecting operation points of a user on the screen, and converting screen coordinates of the operation points into target canvas coordinates on a target canvas; drawing a graph on the target canvas according to the target canvas coordinates of the operation points; and superposing the target canvas drawn with the graph on the video image, characterized in that the video image superposed with the target canvas drawn with the graph is fully displayed on the screen, and the user clicking a start of a graffiti mode triggers an initialization of the target canvas and a requesting of a memory space in a memory for the target canvas, wherein a size of the requested memory space in the memory for the target canvas is determined according to a preset size of the target canvas and an amount of memory per pixel, wherein the preset size of the target canvas is a resolution size of the target canvas, wherein under the condition that the memory space requested for the target canvas in the memory is fixed, the virtual canvas is used as an intermediate state for converting the screen coordinates of the operation points into the target canvas coordinates on the target canvas, which comprises: determining a virtual canvas according to facial features in the video image, a size of the virtual canvas being in a preset proportional relationship with a size of a face area in the video image in which the virtual canvas is square and the width of the virtual canvas is twice the distance between the eyes of a face in the face area in the video image; mapping the screen coordinates of the operation points onto the virtual canvas to obtain virtual canvas coordinates of the operation points; and mapping the virtual canvas coordinates of the operation points onto the target canvas to obtain the target canvas coordinates of the operation points on the target canvas. determining a virtual canvas according to facial features in the video image, a size of the virtual canvas being in a preset proportional relationship with a size of a face area in the video image in which the virtual canvas is square and the width of the virtual canvas is twice the distance between the eyes of a face in the face area in the video image; mapping the screen coordinates of the operation points onto the virtual canvas to obtain virtual canvas coordinates of the operation points; and mapping the virtual canvas coordinates of the operation points onto the target canvas to obtain the target canvas coordinates of the operation points on the target canvas.