Specifies the step of image downsampling used for finding codes at different scales.

Values of this enumeration:

• SuperFast - Low-resolution pyramid for maximum speed
• Fast - Images for different scales are created with downsampling step 2.0
• Precise - Images for different scales are created with downsampling step 1.41
• Strict - Images for different scales are created with downsampling step 1.26
• Extended - Images for different scales are created with downsampling step 1.19