By default, thumbnail images are 216 pixels wide by 274 pixels high. Pixels are calculated by sampling and filtering the input image with each pixel value passed through a contrast curve.
|-w||Specify the width of thumbnail images in pixels.|
|-h||Specify the height of thumbnail images in pixels.|
|-c||Specify a contrast curve to apply in generating the thumbnail images. By default pixels values are passed through a linear contrast curve that simply maps the pixel value ranges. Alternative curves are: exp50 for a 50% exponential curve, exp60 for a 60% exponential curve, exp70 for a 70% exponential curve, exp80 for a 80% exponential curve, exp90 for a 90% exponential curve, exp for a pure exponential curve, linear for a linear curve.|