MemoryStream.Read doesn't copy bytes to buffer - c#

Question

I don't really get it and it's driving me nuts. i've these 4 lines:

Image img = Image.FromFile("F:\\Pulpit\\soa.bmp");
MemoryStream imageStream = new MemoryStream();
img.Save(imageStream, ImageFormat.Bmp);
byte[] contentBuffer = new byte[imageStream.Length];
imageStream.Read(contentBuffer, 0, contentBuffer.Length);

when debugging i can see the bytes values in imageStream. after imageStream.Read i check content of contentBuffer and i see only 255 values. i can't get why is it happening? there is nothing to do wrong in these few lines! if anyone could help me it would be greatly appreciated! thanks, agnieszka

Andrew Kennan · Accepted Answer · 2008-12-17 21:57:22Z

42

Try setting imageStream.Position to 0. When you write to the MemoryStream it moves the Position after the bytes you just wrote so if you try to read there's nothing there.

answered Dec 17, 2008 at 21:57

Andrew Kennan

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Joel Lucsy · Accepted Answer · 2008-12-17 21:56:03Z

27

You need to reset the file pointer.

imageStream.Seek( 0, SeekOrigin.Begin );

Otherwise you're reading from the end of the stream.

answered Dec 17, 2008 at 21:56

Joel Lucsy

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BenAlabaster · Accepted Answer · 2008-12-17 22:00:54Z

15

Add:

imageStream.Position = 0;

right before:

imageStream.Read(contentBuffer, 0, contentBuffer.Length);

the 0 in your read instruction stands for the offset from the current position in the memory stream, not the start of the stream. After the stream has been loaded, the position is at the end. You need to reset it to the beginning.

answered Dec 17, 2008 at 22:00

BenAlabaster

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Patrick Desjardins · Accepted Answer · 2008-12-17 22:04:12Z

8

Image img = Image.FromFile("F:\\Pulpit\\soa.bmp");
MemoryStream imageStream = new MemoryStream();
img.Save(imageStream, ImageFormat.Bmp);
byte[] contentBuffer = new byte[imageStream.Length];
imageStream.Position = 0;//Reset the position at the start
imageStream.Read(contentBuffer, 0, contentBuffer.Length);

answered Dec 17, 2008 at 22:04

Patrick Desjardins

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Jaime Bula · Accepted Answer · 2010-10-17 21:47:48Z

5

Just use

imageStream.ToArray()

It works and it easier.

answered Oct 17, 2010 at 21:47

Jaime Bula

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1 Comment

ZackOfAllTrades Over a year ago

ToArray() creates a new byte[] every time, thus creating garbage, sometimes that's just not okay

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