// Shrink an image so that its longest dimension is no longer than maxSize
func shrinkImage(wand *imagick.MagickWand, maxSize int) (w, h uint) {
w, h = getDimensions(wand)
shrinkBy := 1
if w >= h {
shrinkBy = int(w) / maxSize
} else {
shrinkBy = int(h) / maxSize
}
wand.AdaptiveResizeImage(
uint(int(w)/shrinkBy),
uint(int(h)/shrinkBy),
)
// Sharpen the image to bring back some of the color lost in the shrinking
wand.AdaptiveSharpenImage(0, AdaptiveSharpenVal)
w, h = getDimensions(wand)
return
}