1. Field of the Invention
The present invention relates to a technology for performing a special effect processing for captured images.
2. Description of the Related Art
Some conventional video cameras can perform various special effects on a shot image for reproduction and display. Among these processes, one can perform special effects, in which an image shot by a television camera (e.g., video camera) is mixed with fine and particulate noises characteristic of a film and turned into an image as if it were taken by a picture film camera. This special effect is generally referred to as “film grain.” In the following description, a fine and particulate noise component characteristic of the film added to a camera image is referred to as a “film grain component.” A process for adding a film grain component to an image is referred to as “film grain processing.” Japanese Patent No. 3110763 discusses an image shot by a television camera that is subjected to the film grain processing.
On the other hand, the video camera discussed in Japanese Patent Application Laid-Open No. 11-205754 records a shot image data and information attached thereto regarding the special effect given to the image on a recording medium. When the image data is reproduced, a special effect processing is performed based on the attached information to reproduce the image data. This type of video camera, when recording a shot image, records the image as it is without performing a special effect to the image signal, and records information regarding the special effect as attached information. Then, at the reproducing time, this video camera performs the special effect processing for the reproduced image based on the attached information regarding the special effect, and displays the image.
However, when the film grain processing is performed to the image shot by the video camera, there can be difficulties.
For example, in the case of the video camera discussed in Japanese Patent No. 3110763, the film grain effect sometimes does not emerge appropriately depending on a state of shooting. That is, when an object is dark, the camera unit electrically amplifies signals, so that a lot of random noises are naturally included in the image signals. In that state, if the film grain component is further added, the noise component of the image can become too large, which can cause a degraded image.
On the other hand, some conventional cameras are provided with a function of automatically adjusting an output ration of R (red), G (green), and B (blue) to obtain a stabilized and favorable color reproduction even when a color temperature is changed. That is a so-called white balance function.
Usually, an adjustment of the white balance is performed such that a white object looks white, but there is also a case in which shooting is performed by shifting the adjustment of the white balance a little. For example, in the scene under an incandescent lamp or a sunset color, in some cases the white balance is intentionally shifted a little bit toward a red direction. Thus, an overall image plane is turned into a reddish and warm atmosphere, under which condition shooting is performed. Further, when shooting is performed in a sunrise color or in the shade, there is a case where the white balance is shifted a little bit toward a blue direction. Thus, an overall image plane is turned into a bluish atmosphere, under which condition shooting is performed.
Thus, in some cases, if the film grain component that does not have any deviation in R (red), G (green), and B (blue) is added, the reddish atmosphere or the bluish atmosphere thins out. Even when a film grain processing is carried out in a system performing the special effect based on the attached information at the reproducing time as discussed in Japanese Patent Application Laid-Open No. 11-205754, there is a possibility that such a phenomenon similarly appears.