Stretches the contents of the source rectangle to the destination rectangle with optional resampling.
function StretchRect(const SrcImage: TImageData; SrcX: LongInt; SrcY: LongInt; SrcWidth: LongInt; SrcHeight: LongInt; var DstImage: TImageData; DstX: LongInt; DstY: LongInt; DstWidth: LongInt; DstHeight: LongInt; Filter: TResizeFilter): Boolean;
Imaging (at line 231)
No blending is performed - alpha is simply copied/resampled to destination image. Note that stretching is fastest for images in the same data format (and slowest for images in special formats).