Rotate Image Scanline

unit ScreenRotateScanLine;

interface

uses

Windows, Messages, SysUtils, Classes, Graphics, Controls, Forms, Dialogs,

ExtDlgs, StdCtrls, ExtCtrls, Spin;

type

TFormRotateScanLine = class(TForm)

ImageOriginal: TImage;

ButtonLoad: TButton;

LabelImageInfo: TLabel;

ImageRotated: TImage;

LabelRotateTime: TLabel;

SpinEditThetaDegrees: TSpinEdit;

LabelDegreesClockwise: TLabel;

LabelRotationAngle: TLabel;

LabelCenter: TLabel;

SpinEditI: TSpinEdit;

SpinEditJ: TSpinEdit;

LabelI: TLabel;

LabelJ: TLabel;

CheckBoxStretch: TCheckBox;

SpinEditThetaDegreesHundredths: TSpinEdit;

Label1: TLabel;

OpenPictureDialog: TOpenPictureDialog;

ButtonSaveRotated: TButton;

SavePictureDialog: TSavePictureDialog;

procedure ButtonLoadClick(Sender: TObject);

procedure SpinEditRotate(Sender: TObject);

procedure FormCreate(Sender: TObject);

procedure FormDestroy(Sender: TObject);

procedure CheckBoxStretchClick(Sender: TObject);

procedure ButtonSaveRotatedClick(Sender: TObject);

private

{ Private declarations }

BitmapOriginal: TBitmap;

BitmapRotated : TBitmap;

public

PROCEDURE RotateBitmap;

end;

var

FormRotateScanLine: TFormRotateScanLine;

implementation

{$R *.DFM}

USES

{$IFDEF GIF}

GIFImage, // TGIFImage

{$ENDIF}

GraphicsConversionsLibrary, // LoadGraphicsFile

IniFiles, // TIniFile

ImageLib;

CONST

KeywordSetup = 'Setup';

KeywordDirectory = 'Directory';

// Load 24-bit color image from disk

procedure TFormRotateScanLine.ButtonLoadClick(Sender: TObject);

VAR

Filename: STRING;

NewPath : STRING;

IniFile : TIniFile;

begin

IF OpenPictureDialog.Execute

THEN BEGIN

BitmapOriginal.Free;

BitmapOriginal := LoadGraphicsFile(OpenPictureDialog.Filename);

IF BitmapOriginal.PixelFormat <> pf24bit

THEN BitmapOriginal.PixelFormat := pf24bit; // force to 24 bits

// Update INI file for next time

Filename := ChangeFileExt(ParamStr(0), '.INI');

NewPath := ExtractFilePath(OpenPictureDialog.Filename);

OpenPictureDialog.InitialDir := NewPath;

IniFile := TIniFile.Create(Filename);

TRY

Inifile.WriteString(KeywordSetup, KeywordDirectory, NewPath)

FINALLY

IniFile.Free

END;

// Flush INI cache

WritePrivateProfileString(NIL, NIL, NIL, pChar(Filename));

ImageOriginal.Picture.Graphic := BitmapOriginal;

LabelImageInfo.Caption := IntToStr(BitmapOriginal.Width) + ' by ' +

IntToStr(BitmapOriginal.Height) + ' pixels: ' +

OpenPictureDialog.Filename;

SpinEditI.Value := BitmapOriginal.Width DIV 2;

SpinEditJ.Value := BitmapOriginal.Height DIV 2;

// Rotate and display the image

RotateBitmap

END

end;

// Rotate image by angle[degrees] specified in spinbox

procedure TFormRotateScanLine.SpinEditRotate(Sender: TObject);

begin

RotateBitmap

end;

procedure TFormRotateScanLine.FormCreate(Sender: TObject);

VAR

IniFile : TIniFile;

begin

{$IFDEF GIF}

OpenPictureDialog.Filter := OpenPictureDialog.Filter +

'|GIFs|*.GIF';

{$ENDIF}

IniFile := TIniFile.Create(ChangeFileExt(ParamStr(0), '.INI'));

TRY

OpenPictureDialog.InitialDir := Inifile.ReadString(KeywordSetup,

KeywordDirectory,

ExtractFilePath(ParamStr(0)))

FINALLY

IniFile.Free

END;

BitmapOriginal := TBitmap.Create;

BitmapRotated := TBitmap.Create;

end;

procedure TFormRotateScanLine.FormDestroy(Sender: TObject);

begin

BitmapOriginal.Free;

BitmapRotated.Free

end;

PROCEDURE TFormRotateScanLine.RotateBitmap;

VAR

cosTheta : DOUBLE;

Delta : DWORD; // D3/D4 compatibility

i : INTEGER;

iRotationAxis : INTEGER;

iOriginal : INTEGER;

iPrime : INTEGER;

iPrimeRotated : INTEGER;

j : INTEGER;

jRotationAxis : INTEGER;

jOriginal : INTEGER;

jPrime : INTEGER;

jPrimeRotated : INTEGER;

RowOriginal : pRGBArray;

RowRotated : pRGBArray;

sinTheta : DOUBLE;

StartTime : DWORD;

Theta : DOUBLE; // radians

begin

// The size of BitmapRotated is the same as BitmapOriginal. PixelFormat

// must also match since 24-bit GBR triplets are assumed in ScanLine.

BitmapRotated.Width := BitmapOriginal.Width;

BitmapRotated.Height := BitmapOriginal.Height;

BitmapRotated.PixelFormat := pf24bit;

// "Start" the clock

StartTime := GetTickCount;

// Axis of rotation is normally center of image

TRY

iRotationAxis := SpinEditI.Value

EXCEPT

iRotationAxis := 0

END;

TRY

jRotationAxis := SpinEditJ.Value

EXCEPT

jRotationAxis := 0

END;

// Convert degrees to radians. Use minus sign to force clockwise rotation.

Theta := -(SpinEditThetaDegrees.Value +

SpinEditThetaDegreesHundredths.Value/100) *

PI / 180;

sinTheta := SIN(Theta);

cosTheta := COS(Theta);

// Step through each row of rotated image.

FOR j := BitmapRotated.Height-1 DOWNTO 0 DO

BEGIN

RowRotated := BitmapRotated.Scanline[j];

// Assume the bitmap has an even number of pixels in both dimensions and

// the axis of rotation is to be the exact middle of the image -- so this

// axis of rotation is not at the middle of any pixel.

// The transformation (i,j) to (iPrime, jPrime) puts the center of each

// pixel at odd-numbered coordinates. The left and right sides of each

// pixel (as well as the top and bottom) then have even-numbered coordinates.

// The point (iRotationAxis, jRotationAxis) identifies the axis of rotation.

// For a 640 x 480 pixel image, the center point is (320, 240). Pixels

// numbered (index i) 0..319 are left of this point along the "X" axis and

// pixels numbered 320..639 are right of this point. Likewise, vertically

// pixels are numbered (index j) 0..239 above the axis of rotation and

// 240..479 below the axis of rotation.

// The subtraction (i, j) - (iRotationAxis, jRotationAxis) moves the axis of

// rotation from (i, j) to (iRotationAxis, jRotationAxis), which is the

// center of the bitmap in this implementation.

jPrime := 2*(j - jRotationAxis) + 1;

FOR i := BitmapRotated.Width-1 DOWNTO 0 DO

BEGIN

iPrime := 2*(i - iRotationAxis) + 1;

// Rotate (iPrime, jPrime) to location of desired pixel

// Note: There is negligible difference between floating point and

// scaled integer arithmetic here, so keep the math simple (and readable).

iPrimeRotated := ROUND(iPrime * CosTheta - jPrime * sinTheta);

jPrimeRotated := ROUND(iPrime * sinTheta + jPrime * cosTheta);

// Transform back to pixel coordinates of image, including translation

// of origin from axis of rotation to origin of image.

iOriginal := (iPrimeRotated - 1) DIV 2 + iRotationAxis;

jOriginal := (jPrimeRotated - 1) DIV 2 + jRotationAxis;

// Make sure (iOriginal, jOriginal) is in BitmapOriginal. If not,

// assign blue color to corner points.

IF (iOriginal >= 0) AND (iOriginal <= BitmapOriginal.Width-1) AND

(jOriginal >= 0) AND (jOriginal <= BitmapOriginal.Height-1)

THEN BEGIN

// Assign pixel from rotated space to current pixel in BitmapRotated

RowOriginal := BitmapOriginal.Scanline[jOriginal];

RowRotated[i] := RowOriginal[iOriginal]

END

ELSE BEGIN

RowRotated[i].rgbtBlue := 255; // assign "corner" color

RowRotated[i].rgbtGreen := 0;

RowRotated[i].rgbtRed := 0

END

END

END;

Delta := GetTickCount - StartTime; // "stop" the clock

LabelRotateTime.Caption := 'Rotation Time = ' + IntToStr(Delta) + ' ms';

ImageRotated.Picture.Graphic := BitmapRotated

END {RotateImage};

procedure TFormRotateScanLine.CheckBoxStretchClick(Sender: TObject);

begin

ImageOriginal.Stretch := CheckBoxStretch.Checked;

ImageRotated.Stretch := CheckBoxStretch.Checked

end;

procedure TFormRotateScanLine.ButtonSaveRotatedClick(Sender: TObject);

begin

IF SavePictureDialog.Execute

THEN BitmapRotated.SaveToFile(SavePictureDialog.Filename)

end;

end.