Hello,
Is there a technical reason why in packages/fcl-image/src/fpreadjpeg.pas
the scale option is commented / not implemented?
I've changed that unit for my purpose (see attachment. I hope the patch
is valid, I don't have a svn fpc, so it's hand edited).
I have to create thumbnail images and found, that pre-scaling via
fpreadjpeg.pas makes loading the images a lot faster.
Of course resampling to the final size is faster too.
The idea of the attached code is, to set MinWidth/MinHeight to the size
of the desired thumbnail.
The image is pre-shrunk this way (still always bigger than thumbnail)
and can be resampled afterwards via stretch draw.
Any problems to expect?
Thank you
Best regards
Theo
Index: packages/fcl-image/src/fpreadjpeg.pas
===================================================================
--- packages/fcl-image/src/fpreadjpeg.pas (Revision 13963)
+++ packages/fcl-image/src/fpreadjpeg.pas (Arbeitskopie)
@@ -48,6 +51,8 @@
TFPReaderJPEG = class(TFPCustomImageReader)
private
FSmoothing: boolean;
+ FMinHeight:integer;
+ FMinWidth:integer;
FWidth: Integer;
FHeight: Integer;
FGrayscale: boolean;
@@ -69,6 +74,9 @@
property ProgressiveEncoding: boolean read FProgressiveEncoding;
property Smoothing: boolean read FSmoothing write SetSmoothing;
property Performance: TJPEGReadPerformance read FPerformance write SetPerformance;
+ property Scale: TJPEGScale read FScale write FScale;
+ property MinWidth:integer read FMinWidth write FMinWidth;
+ property MinHeight:integer read FMinHeight write FMinHeight;
end;
implementation
@@ -177,9 +185,28 @@
end;
procedure InitReadingPixels;
+ var d1,d2:integer;
+
+ function DToScale(inp:integer):TJPEGScale;
+ begin
+ if inp>7 then Result:=jsEighth else
+ if inp>3 then Result:=jsQuarter else
+ if inp>1 then Result:=jsHalf else
+ Result:=jsFullSize;
+ end;
+
begin
FInfo.scale_num := 1;
- FInfo.scale_denom := 1;// shl Byte(FScale);
+
+ if (FMinWidth>0) and (FMinHeight>0) then
+ if (FInfo.image_width>FMinWidth) or (FInfo.image_height>FMinHeight) then
+ begin
+ d1:=Round((FInfo.image_width / FMinWidth)-0.5);
+ d2:=Round((FInfo.image_height / FMinHeight)-0.5);
+ if d1>d2 then fScale:=DToScale(d2) else fScale:=DtoScale(d1);
+ end;
+
+ FInfo.scale_denom :=1 shl Byte(FScale); //1
FInfo.do_block_smoothing := FSmoothing;
if FGrayscale then FInfo.out_color_space := JCS_GRAYSCALE;_______________________________________________
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