TIOParams.JPEG_Quality

Declaration

property JPEG_Quality: integer;

Description

The quality factor for the current JPEG image. Range is 1 to 100, though typical range is 60 (low quality) to 95 (high quality).
Higher values will improve image quality but require more disk space.

Notes:
- This property is not stored in a JPEG image, so it is never set when loading an image. Instead you set it when saving a JPEG to specify your desired compression.
- It is possible to estimate the original JPEG compression using IECalcJpegStreamQuality or IECalcJpegFileQuality.

Default: 80 (Specified by IOParamDefaults)

Quality Comparison

// Test Code
var
  i, qual: Integer;
  bmp: TIEBitmap;
begin
  for i := 1 to 20 do
  begin
    qual := i * 5;
    bmp := TIEBitmap.Create;
    bmp.ParamsEnabled := True;
    bmp.Read( TestFilename );
    bmp.Params.JPEG_Quality := qual;
    bmp.Write( 'Test_'+IntToStr( qual )+'.jpg' );
    bmp.Free;

    bmp := TIEBitmap.Create;
    bmp.Read( 'Test_'+IntToStr( qual )+'.jpg' );
    bmp.Resample( 2.0 );
    bmp.Crop( MulDiv( bmp.Width, 1, 4 ), MulDiv( bmp.Height, 1, 4 ), MulDiv( bmp.Width, 3, 4 ), MulDiv( bmp.Height, 3, 4 ));
    bmp.Write( '_'+IntToStr( qual )+'.png' );
    bmp.Free;
  end;
end;

TestImage1.png

TestImage2.png

Examples

// Load a JPEG and save it using the same compression quality
ImageEnView1.IO.LoadFromFile('C:\input.jpg');
ImageEnView1.IO.Params.JPEG_Quality := IECalcJpegFileQuality('C:\input.jpg');
ImageEnView1.IO.SaveToFile('D:\output.jpg');

// Convert a BMP to a JPEG at 90% quality
bmp := TIEBitmap.create;
bmp.ParamsEnabled := True;
bmp.Read( 'D:\input.bmp' );
bmp.Params.JPEG_Quality := 90;
bmp.Write( 'D:\output.jpg' );
bmp.Free;

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