TmemoryStream Read/write [resolved]
lazarus / 8-Other

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didiergm · 2009-07-22 19:37

Hello,

Before loading a jpeg, I need to be able to read and do a few checks
and changes on the fly then pass the result to  a timage.Picture;

So I load a jpeg into a tmemorystream; do a series of readbuffer into
an array [1..128] of bytes but when I come to do a
Image.picture.loadfromstreamwithExt (m, '.jpg') I get an I/O error 103
file is not opened. and I fail to understand why it is doing this.

If I do not touch the Memorystream (ie m.LoadfromFile then
Image.picture.loadfromstreamwithExt (m, '.jpg')) for testing
everything is right.

So my question is can I read and write into a single tmemorystream ?
could the I/O error 103 indicate that the JPG format is wrong ? (ie
I've got a bug in my logic ?)

thanks in advance

Didier

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theo · 2009-07-22 20:27

A wild guess:

m.position:=0;

before passing to loadfromstreamwithExt

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didiergm · 2009-07-22 21:53

Theo,

Done that, no change; but I am 99% there; I found a bug in my logic
which was destroying the JPG structure. So I suspect the I/O error 103
is misleading and means in that case something like 'bad format'


thanks for your help
Didier

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theo · 2009-07-22 22:06

I don't know.
I have no problems doing this:

Code: [Select]procedure TForm1.Button1Click(Sender: TObject);
var
  m: TMemoryStream;
  a:array[1..128] of byte;
begin
 m:=TMemoryStream.create;
 m.LoadFromFile('/home/theo/Documents/2009-01-01-185110.jpg');
 m.Read(a,127);
 m.Position:=0;
 Image1.picture.LoadFromStreamWithFileExt(m, '.jpg');
 m.free;
end;

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didiergm · 2009-07-22 22:26

Theo,

I confirm this was my (twisted ?) logic corrupting the jpg. I am
writing an application that voluntarily corrupts a jpeg and restores
it before display.

Didier