ImageEn, unit imageenproc




procedure Rotate(Angle: Double; AntiAliasMode: TIEAntialiasMode = ierFast; BackgroundColor: TColor = -1);


Rotate the current image by the specified angle (negative or positive degrees counter-clockwise).

AntialiasMode specifies the algorithm used to improve rotation quality (only used when angle is NOT 90, 180 or 270):
Value Description
ierNone No anti-aliasing (lowest quality)
ierFast Fast, but lower quality
ierBilinear Bilinear, high quality
ierBicubic Bicubic, highest quality

BackgroundColor specifies an alternative background color to fill new regions (i.e. when not rotating at a 90 degree angle). It is not used if the image contains an alpha channel.
If -1, Rotate uses the default background. If clNone, then an alpha channel is applied to the image and the non-image area will become transparent.

This is a common image from a digital camera that was not held correctly causing the horizon not to be level.

After calling ImageEnView1.Proc.Rotate( 5 ):

 If the image has an alpha channel then the null area is filled with transparency (so you will not see the background color). To prevent the transparent area, and force a background color fill, remove the alpha channel
 To crop the image caused by rotation, use RotateAndCrop
 To crop and rotate an ROI, use Crop
 To allow the user to interactively rotate the image, use RotateTool
 If PdfViewer is enabled, this will redirect to PageRotation
 A UI for this is available to your users in the Image Processing dialog
 For very large images, ierFast can be memory intensive. Use ierNone or one of the other modes instead

Anti-alias Modes


Demo  Demos\ImageEditing\CompleteEditor\PhotoEn.dpr
Demo  Demos\ImageEditing\EveryMethod\EveryMethod.dpr


// Rotate the image 45 clockwise at highest quality and using the ImageEnView background color
ImageEnView1.Proc.Rotate( 315, ierBicubic, -1 );

// Rotate the image 90 clockwise (Note: AntialiasMode is irrelevant for 90 deg. rotations)
ImageEnView1.Proc.Rotate( 270 );

// Rotate the image 180 clockwise
ImageEnView1.Proc.Rotate( 180 );

// Rotate the image 90 counter-clockwise
ImageEnView1.Proc.Rotate( 90 );

// Rotate the image 45 clockwise at highest quality and make the non-image area transparent
ImageEnView1.Proc.Rotate( 315, ierBicubic, clNone );

// Which is the same as...

// Rotate the image 45 clockwise, with good quality, and the null area created by the rotation set as transparent
ImageEnView1.IEBitmap.AlphaChannel; // Create an alpha channel if one does not exist
ImageEnView1.Proc.Rotate( -45, ierBicubic );

// Rotate the image 45 clockwise, with good quality, and the null area created by the rotation set as black
ImageEnView1.IEBitmap.RemoveAlphaChannel; // Remove alpha channel if there is one
ImageEnView1.Proc.Rotate( -45, ierBicubic, clBlack );

// Load and rotate an image 90 counter-clockwise
ImageEnView1.IO.LoadFromFile( 'D:\TestImage.jpg' );

ImageEnView1.Proc.Rotate( 90 );

See Also

 Global Image Methods