ImageEn, unit iexBitmaps

JpegLosslessTransform


Declaration

function JpegLosslessTransform(const SourceFile, DestFile: WideString; Transform: TIEJpegTransform; UpdateEXIF: Boolean = True): boolean; overload;
function JpegLosslessTransform(const SourceFile, DestFile: WideString; Transform: TIEJpegTransform; GrayScale: Boolean; CopyMarkers: TIEJpegCopyMarkers; CutRect: TRect; UpdateEXIF: Boolean = True): Boolean; overload;
function JpegLosslessTransform(const SourceFile, DestFile: WideString; RotateAngle: Integer; UpdateEXIF: Boolean = True): boolean; overload;
function JpegLosslessTransform(const SourceFile, DestFile: WideString; Direction: TFlipDir; UpdateEXIF: Boolean = True): boolean; overload;


Description

Losslessly rotates, flips or crops (cuts) a JPEG file.


Description

Parameter Description
SourceFile The full path and filename of the source file
DestFile The full path and filename for the resulting file
Transform The transformation to perform
GrayScale True force grayscale output
CopyMarkers How comments and markers (e.g. IPTC info) should be copied (Default: jcCopyAll)
CutRect Specifies the rectangle to retain when Transform = jtCut
UpdateEXIF Updates the EXIF thumbnail and orientation tags

Returns false if the operation failed.

Notes:
- Rotation direction is the opposite to standard ImageEn Rotate. jtRotate90 means rotate 90 clockwise
- With RotateAngle overload, RotateAngle is a standard ImageEn rotation angle, e.g. 90 means rotate 90 counter-clockwise. Values other than -90, 90, 180, -180, 270 and -270 are ignored

See also: JpegLosslessTransform2 which works with a single file.


Lossless Information

Whenever you save a JPEG by regular methods it needs to re-encoded, so after multiple re-saves the quality can become quite degraded. Lossless JPEG operations, on the other hand, work by rearranging the compressed data, without ever fully decoding the image, therefore there is no degration in quality.
Note, however, that lossless operations can only work on full DCT blocks, so when cutting/cropping the resulting image may contain at least a part of the area outside CutRect depending on the need to align with to the nearest DCT block boundary (or multiple blocks, depending on the sampling factors).


Demo

Demo  Demos\ImageEditing\LosslessJpegEdit\Lossless.dpr


Examples

// Rotate input.jpg 90 clockwise and save to output.jpg
JpegLosslessTransform('D:\input.jpg', 'D:\output.jpg', jtRotate90, false, jcCopyAll, Rect(0, 0, 0, 0));

// Rotate input.jpeg 90 clockwise and save to output.jpeg
JPEGLosslessRotateFile('D:\input.jpeg', 'D:\output.jpeg', 270);