Re: Once and for all! Fastest way to load large jpeg
- From: erewhon@xxxxxxxxxx (J French)
- Date: Thu, 14 Dec 2006 09:44:29 GMT
On 13 Dec 2006 21:42:50 -0800, jimbo@xxxxxxxxxx wrote:
<snip>
How about kicking off a separate App that generates the thumbnails in
the back ground, that way you'll be using the processor while the user
is twiddling with the mouse.
The thumbs are no problem.
<snip>
User chooses folder from directorylistbox populating a filelistbox.
I create an object for each entry with path and other relevant info and
add it to an array with a common index to the filelistbox. So I use
whichever is convenient.
Where exactly are those JPEGs coming from
CD USB or any external drive.
How long do you want to keep the JPEGs
<snip>In practice only long enough to assign it to the larger TImage. I free
it immediately. See original example.
Could you explain the 4mb
- do you mean that a 4mb file is slow to load ?
Yes from external media. I orginally tested with 2MB files from various
cameras. When I started testing with larger 4MB+ files the speed is
borderline acceptable. I need to improve loading the image from disk
somehow in order to properly support large files.
If that is the case, you could try reading the entire file into a
memory stream and then use LoadFromStream
- I'm not sure, but it could cut down on physical disk reads
I found this. Would this help?
var
bm2: TBitmap;
st: TMemoryStream;
begin
bm2:= TBitmap.Create;
bm2.PixelFormat := pf24bit;
bm2.Width := 256 ;
bm2.Height := 256 ;
st := TMemoryStream.Create;
bm2.SaveToStream (st);
st.Seek( - (256*256*3), soFromEnd);
st.WriteBuffer( ColorArray[ScrollPos,0,0,1] , 256*256*3);
st.Seek(0, soFromBeginning );
bm2.LoadFromStream(st);
Image1.Picture.Bitmap := bm2;
bm2.Destroy ;
st.Destroy;
end;
The above code is just creating a sort of emptyish Bitmap and shoving
it into an Image.
What I would do is to take one of your large Bitmaps, load it into a
TMemoryStream then load the image from the TMemoryStream
If you have FileMon, you could check how many file reads are made on
the jpg on the CD - it might well be that there are hundreds of them
Things like this are normally slow because of excessive disk activity.
You also might try looking for a TBufferedStream component, I wrote
one some time ago, but being an idiot did not descend it from an
abstract TStream. I'm too ashamed to post or distribute it.
The improvement in reading and writing speeds was incredible.
.
- References:
- Once and for all! Fastest way to load large jpeg
- From: jimbo
- Re: Once and for all! Fastest way to load large jpeg
- From: J French
- Re: Once and for all! Fastest way to load large jpeg
- From: jimbo
- Re: Once and for all! Fastest way to load large jpeg
- From: J French
- Re: Once and for all! Fastest way to load large jpeg
- From: jimbo
- Re: Once and for all! Fastest way to load large jpeg
- From: J French
- Re: Once and for all! Fastest way to load large jpeg
- From: jimbo
- Re: Once and for all! Fastest way to load large jpeg
- From: J French
- Re: Once and for all! Fastest way to load large jpeg
- From: jimbo
- Once and for all! Fastest way to load large jpeg
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