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Rotate + Crop versus Crop with angle

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T O P I C R E V I E W
LikeMike	Posted - Apr 24 2022 : 11:56:03 Hello! There is something wrong with the Crop-function. If I use: Img.Proc.Rotate(45); Img.Proc.Crop(Rect.Left, Rect.Top,Rect.Right, Rect.Bottom ); I get the expected result. If I use: Img.Proc.Crop(Rect, 45, ierFast); The result is not what I expected. 1. the orientation of the rotation is different (Rotate : counterclockwise, Crop : clockwise) 2. even if I set the second code to 315° the cutout is not the same! The problem is: the first code is much slower than the second one, so it would be nice, if Crop(rect, angle, ..) gives the same result. Regards Mike
5 L A T E S T R E P L I E S (Newest First)
xequte	Posted - May 03 2022 : 23:21:04 I have improved the help documentation with a better explanation... The Rotate and Crop overload rotates the whole image and the crops to a region of interest by adjusting the crop region to account for the rotation. Consider this image: And these parameters: const Rotation_Angle = 10; Crop_Left = 220; Crop_Top = 70; Crop_Right = 220 + 170; Crop_Bottom = 70 + 160; Cropping then rotating: ImageEnView1.IO.LoadFromFile( 'D:\Tiger.jpg' ); ImageEnView1.Proc.Crop( Crop_Left, Crop_Top, Crop_Right, Crop_Bottom ); ImageEnView1.Proc.Rotate( Rotation_Angle, ierBicubic, clBlack ); Rotating then cropping: ImageEnView1.IO.LoadFromFile( 'D:\Tiger.jpg' ); // Note the negative rotation value ImageEnView1.Proc.Crop( Rect( Crop_Left, Crop_Top, Crop_Right, Crop_Bottom ), -Rotation_Angle, ierBicubic ); Nigel Xequte Software www.imageen.com
LikeMike	Posted - Apr 28 2022 : 01:11:43 Yes - that's exactly my problem...
xequte	Posted - Apr 27 2022 : 21:53:26 Hi It would be difficult to get the same code using the rotate overload, because you won't know the size of the image until after it has been rotated (i.e. left and top of the crop rect would have to be shifted by an [as yet] unknown amount). Nigel Xequte Software www.imageen.com
LikeMike	Posted - Apr 26 2022 : 03:50:46 2. That's correct. They use a different method of cropping OK - and what do I have to change here "Img.Proc.Crop(Rect, 45, ierFast);" to get the same result?
xequte	Posted - Apr 25 2022 : 22:00:48 Hi Mike 1. Unfortunately for historical reasons there is some inconsistency with the directions of rotation values in ImageEn. For crop, the rotation direction is clockwise. 2. That's correct. They use a different method of cropping Nigel Xequte Software www.imageen.com