Adjusting image quality when resizingRSS

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  desertfoxaz

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  Adjusting image quality when resizing

  Sep 19, 2011 05:12 PM|desertfoxaz|LINK

  I'm trying to refactor some image resizing code to make it more efficient.  I have the resizing working fine, however the resulting image's bytes are a bit larger than the original code's results.

  I have the following code

  private Bitmap ResizeImage(Bitmap originalImage, int width, int height)
  {
  	Bitmap finalImage = new Bitmap(width, height);
  
  	using (Graphics graphics = Graphics.FromImage(finalImage))
  	{
  		Rectangle rectangle = new Rectangle(0, 0, width, height);
  
  		graphics.CompositingQuality = CompositingQuality.Default;
  		graphics.SmoothingMode = SmoothingMode.None;
  		graphics.InterpolationMode = InterpolationMode.Bilinear;
  
  		graphics.DrawImage(originalImage, rectangle);
  	}
  
  	const int quality = 40;
  
  	ImageCodecInfo codec = RetrieveCodec("image/jpeg");
  
  	using (EncoderParameters codeParams = new EncoderParameters())
  	{
  		using (EncoderParameter p = new EncoderParameter(Encoder.Quality, quality))
  		{
  			using (MemoryStream bmpStream = new MemoryStream())
  			{
  				codeParams.Param[0] = p;
  
  				// Exception occurs here
  				finalImage.Save(bmpStream, codec, codeParams);
  			}
  		}
  	}
  
  	return finalImage;
  }
  
  private ImageCodecInfo RetrieveCodec(string mimeType)
  {
  	ImageCodecInfo[] codecs = ImageCodecInfo.GetImageEncoders();
  
  	foreach (ImageCodecInfo codec in codecs)
  	{
  		if (codec.MimeType == mimeType)
  			return codec;
  	}
  
  	return null;
  }

   

  When I call finalImage.Save(bmpStream, codec, codeParams), I get an Argument exception.  What am I doing wrong?  I checked the arguments and it seems everything has the right values.

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  desertfoxaz

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  96 Points

  422 Posts

  Re: Adjusting image quality when resizing

  Sep 21, 2011 03:59 PM|desertfoxaz|LINK

  Figured it out.  Apparently I wasn't copying the bitmap with "originalImage = resizedBmp;"

  private Bitmap ResizeImage(Bitmap originalImage, int width, int height)
  {
  	using (Bitmap resizedBmp = new Bitmap(width, height))
  	{
  		using (Graphics g = Graphics.FromImage(resizedBmp))
  		{
  			g.CompositingQuality = CompositingQuality.Default;
  			g.SmoothingMode = SmoothingMode.None;
  			g.InterpolationMode = InterpolationMode.Bilinear;
  
  			Rectangle bounds = new Rectangle(0, 0, width, height);
  			g.DrawImage(originalImage, bounds);
  		}
  
  		originalImage = resizedBmp;
  
  		const int quality = 40;
  
  		ImageCodecInfo codec = RetrieveCodec("image/jpeg");
  
  		using (MemoryStream bmpStream = new MemoryStream())
  		{
  			using (EncoderParameters codecParams = new EncoderParameters())
  			{
  				using (EncoderParameter p = new EncoderParameter(Encoder.Quality, quality))
  				{
  					codecParams.Param[0] = p;
  					resizedBmp.Save(bmpStream, codec, codecParams);
  				}
  			}
  
  			return new Bitmap(bmpStream);
  		}
  	}
  }

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  desertfoxaz

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  96 Points

  422 Posts

  Re: Adjusting image quality when resizing

  Sep 21, 2011 04:08 PM|desertfoxaz|LINK

  That wasn't it.  I'm still getting the same exception.  The code changes I made were not being executed...

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  desertfoxaz

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  422 Posts

  Re: Adjusting image quality when resizing

  Sep 21, 2011 04:48 PM|desertfoxaz|LINK

  Here's what that problem was.  I am not sure why it is happening though.

  I was declaring const int quality = 40.  When I created my EncoderParameter "p", the codecParams[0].Type was set to EncoderParameterValueType.ValyeTypeByte and that was apparently causing the argument exception.  One of two changes fixes it:

  1. Instead of declaring quality as an integer constant, declare it as an integer variable
  2. Or declare quality as a long constant

  If I do either, the codecParams[0].Type is set to EncoderParameterValue.Type.ValueTypeLong.

  Why would declaring it as an integer constant try to make it a byte and declaring it as an integer variable not?