/// <summary>
/// Determines the size of the source image.
/// This method is only used when re-projection applies.
/// </summary>
/// <param name="sourceBoundingBox">The source bounding box.</param>
/// <param name="targetSize">Requested target size.</param>
/// <returns>The computed source size.</returns>
protected virtual Size DetermineSourceSize(IBoundingBox sourceBoundingBox, Size targetSize)
{
if (!ReprojectionServiceOptions.SourceSizeFactor.HasValue)
{
return(DetermineSourceSizeByAmountOfPixels(sourceBoundingBox, targetSize.Area()));
}
if (ReprojectionServiceOptions.SourceSizeFactor.Value < 0)
{
return(DetermineSourceSizeByAmountOfPixels(sourceBoundingBox, -ReprojectionServiceOptions.SourceSizeFactor.Value * targetSize.Area()));
}
var aspect = sourceBoundingBox.AspectRatio();
var sizes = new [] {
new SizeD(targetSize.Height * aspect, targetSize.Height),
new SizeD(targetSize.Width * aspect, targetSize.Width),
new SizeD(targetSize.Width, targetSize.Width / aspect),
new SizeD(targetSize.Height, targetSize.Height / aspect)
};
var min = sizes.Select(s => s.Area()).Min();
var max = sizes.Select(s => s.Area()).Max();
return(DetermineSourceSizeByAmountOfPixels(sourceBoundingBox, min + (max - min) * ReprojectionServiceOptions.SourceSizeFactor.Value));
}
/// <summary>
/// Knowing the source bounding box and its aspect ratio, this helper determines
/// an image size given the an amount of pixels that the image should contain.
/// </summary>
/// <param name="sourceBoundingBox">The source bounding box</param>
/// <param name="nPixels">The number of pixels that the image should contain</param>
/// <returns>The size determined out of bounding box and number of pixels, rounded to the nearest integer.</returns>
protected virtual Size DetermineSourceSizeByAmountOfPixels(IBoundingBox sourceBoundingBox, double nPixels)
{
var aspectRatio = sourceBoundingBox.AspectRatio();
var h = Math.Sqrt(nPixels / aspectRatio);
var w = h * aspectRatio;
return(new Size((int)Math.Round(w), (int)Math.Round(h)));
}
/// <summary> Determines if two bounding boxes have the same aspect ratio. </summary>
/// <param name="this">First bounding box.</param>
/// <param name="other">Second bounding box.</param>
/// <returns>True, if the aspect ratio is equal. False otherwise.</returns>
public static bool EqualsAspect(this IBoundingBox @this, IBoundingBox other)
{
return(Math.Abs(@this.AspectRatio() - other.AspectRatio()) < 1e-4);
}