// MultiScale searches an image at multiple scales and performs non-max suppression.
//
// At each level, the image is rescaled using Interp,
// then padded using Pad before calling Transform.Apply().
// The levels are geometrically spaced at intervals of PyrStep.
// Detections are filtered using DetFilter and then non-max suppression
// is performed using the OverlapFunc test.
func MultiScale(im image.Image, scorer slide.Scorer, shape PadRect, opts MultiScaleOpts) ([]Det, MultiScaleDuration, error) {
scales := imgpyr.Scales(im.Bounds().Size(), scorer.Size(), opts.MaxScale, opts.PyrStep).Elems()
ims := imgpyr.NewGenerator(im, scales, opts.Interp)
pyr := featpyr.NewGenerator(ims, opts.Transform, opts.Pad)
var dets []Det
l, err := pyr.First()
if err != nil {
return nil, MultiScaleDuration{}, err
}
var dur MultiScaleDuration
for l != nil {
t := time.Now()
pts, err := Points(l.Feat, scorer, opts.DetFilter.LocalMax, opts.DetFilter.MinScore)
if err != nil {
return nil, MultiScaleDuration{}, err
}
dur.Slide += time.Since(t)
// Convert to scored rectangles in the image.
for _, pt := range pts {
rect := pyr.ToImageRect(l.Image.Index, pt.Point, shape.Int)
dets = append(dets, Det{pt.Score, rect})
}
l, err = pyr.Next(l)
if err != nil {
return nil, MultiScaleDuration{}, err
}
}
dur.Resize = pyr.DurResize
dur.Feat = pyr.DurFeat
t := time.Now()
Sort(dets)
dets = Suppress(dets, opts.SupprFilter.MaxNum, opts.SupprFilter.Overlap)
dur.Suppr = time.Since(t)
return dets, dur, nil
}
// Returns scored windows in image.
// Windows are represented by the position of their top-left corner in the feature pyramid.
func detectPyrPoints(pyr *featpyr.Pyramid, scorer slide.Scorer, localmax bool, minscore float64) ([]pyrDetPos, error) {
var dets []pyrDetPos
size := scorer.Size()
for level, im := range pyr.Feats {
if im.Width < size.X || im.Height < size.Y {
break
}
// Get points from each level.
imdets, err := Points(im, scorer, localmax, minscore)
if err != nil {
return nil, err
}
// Append level to each point.
for _, imdet := range imdets {
pyrpt := imgpyr.Point{level, imdet.Point}
dets = append(dets, pyrDetPos{imdet.Score, pyrpt})
}
}
return dets, nil
}