座標(x, y)のピクセルのカラーを取得します
If the pixel coordinates are out of bounds (larger than width/height or small than 0),
they will be clamped or repeat based on the texture's wrap mode.
If you are reading a large block of pixels from the texture, it may be faster
to use GetPixels which returns a whole block of pixel colors.
Note: For depth data based WebCamTexture instances, the depth value (distance in meters) can be accessed using the Color.r property. See Also: WebCamTexture.isDepth.