I am trying to simulate a long exposure photo by combining images(frames) into one image and by performing operations based on a preset alpha. I am doing this on an iPhone, and I currently have the length of the video set to 1 second(30 frames). The alpha is set to `1.0/frameCount` however I hard coded in 30 to represent one second of 30 FPS video capture. I stop the operations once it has reached one second of video/30 frames. The idea is the user can set a timer for x seconds and I will do the math to figure out how many frames to allow.
Here is the code I am using:
- (void)processImage:(Mat&)image
{
if (_isRecording) {
// first frame
double alpha = 1.0/30;
if (_frameCount == 0) {
_exposed = image;
_frameCount++;
} else {
Mat exposed = _exposed.clone();
addWeighted(exposed, alpha, image, 1.0 - alpha, 0.0, _exposed);
_frameCount++;
}
// stop and save image
if (_frameCount == 30) {
_isRecording = NO;
_frameCount = 0;
cvtColor(_exposed, _exposed, CV_BGRA2RGB, 30);
UIImage *exposed = [LEMatConverter UIImageFromCVMat:_exposed];
UIImageWriteToSavedPhotosAlbum(exposed, nil, nil, nil);
NSLog(@"saved");
}
}
}
When I run this code I basically get back a still image that looks as if it is a single frame. Here is an example:
![enter image description here][1]
Does anyone know how I can produce the desired effect of a long exposure image from video frames given I know how many frames there will be?
[1]: http://i.stack.imgur.com/bFw49.jpg
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