Пример #1
0
func useLossless(image *vips.Image, options SaveOptions) bool {
	if !options.Lossless {
		return false
	}

	if !options.LossyIfPhoto {
		return true
	}

	// Mobile devices start being unwilling to load >= 3 megapixel PNGs.
	// Also we don't want to bother to edge detect on large images.
	if image.Xsize()*image.Ysize() >= 3*1024*1024 {
		return false
	}

	// Take a histogram of a Sobel edge detect of our image.  What's the
	// highest number of histogram values in a row that are more than 1%
	// of the maximum value? Above 16 indicates a photo.
	metric, err := image.PhotoMetric(0.01)
	return err != nil || metric < 16
}