ImageEn, unit imageenproc

TImageEnProc.Crop

TImageEnProc.Crop


Declaration

// Standard overload
procedure Crop(x1, y1, x2, y2 : Integer);

// TRect overload
procedure Crop(Rect : TRect);

// TRect with rotation overload. Angles are degrees clockwise
procedure Crop(Rect: TRect; Rotation: double; AntialiasMode: TIEAntialiasMode = ierFast);

// Perspective fix overload
procedure Crop(Quadrilater: array of TDPoint); overload;


Description

Replace the current image with that within the specified rectangle (i.e. keep only the specified region).

The Perspective fix overload allows you to adjust images that have perspective distortion. You need to specify the four points that will become the corners of the new image. The order is as follows:
- Top-Left corner
- Top-right corner
- Bottom-right corner
- Bottom-Left corner



Notes:
- Negative or out-of-range values will enlarge the image. FillColor will be used for the new areas. If -1, the default background is used. If clNone, then the non-image area will become transparent.
- Use CropSel to crop to the current selection
- This function is also available to the user in the Image Processing dialog


Rotate and Crop 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 );




Examples

// Crop the image at position, Top-Left: (20, 20), Bottom-right: (100, 100). The resulting image will be 80 x 80 pixels
ImageEnView1.Proc.Crop( 20, 20, 100, 100 );

// Crop to the selected area of the image (same as ImageEnView1.Proc.CropSel)
ImageEnView1.Proc.Crop( ImageEnView1.SelectedRect.x,
                        ImageEnView1.SelectedRect.y,
                        ImageEnView1.SelectedRect.x + ImageEnView1.SelectedRect.Width,
                        ImageEnView1.SelectedRect.y + ImageEnView1.SelectedRect.Height );

// Crop to the rect(100, 100, 300, 200) and rotate image 20 deg. Clock-wise
ImageEnView1.Proc.Crop( rect( 100, 100, 300, 200 ), 20, ierBicubic );

// Crops to the specified quadrilateral (4 points that will become the new corners) and applies forward perspective mapping. Useful to adjust perspective distortion
ImageEnView1.Proc.Crop([ DPoint(104, 85), // Top-Left corner
                         DPoint(1000, 150), // Top-right corner
                         DPoint(181, 500), // Bottom-right corner
                         DPoint(54, 400) // Bottom-Left corner
                        ]);

// Fix a parallelogram
ImageEnView1.Proc.Crop([ DPoint(50, 0), DPoint(500, 0), DPoint(450, 400), DPoint(0, 400)]);




See Also

- CropSel
- Global Image Methods