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Determine size of image in memory

I have a .Net 4 Windows Forms project created with Visual Studio 2010 using c#.

I need to open an image file (jpg or gif) and resize the dimensions to a fixed size and then adjust the quality of the image until the image size is 30kb or less. Is there a way to calculate the memory used by this image while in memory? I don't want the overhead of saving it to disk to check System.IO.FileInfo. I would be happy to use a free library or utility which would help.

Scott

Carlos Villegas

Hello, I know how to do that for jpg files, but for gif files... I think that is more complex because to control the quality (therefore the file size) you need to play with the color palette... the next code can help you to control the size of your jpg files:

private void TestExample()
{
    ResizeImage(@"C:\Temp\MyOriginalImage.jpg", @"C:\Temp\MyResizedImage.jpg", 640, 30000);
}

private void ResizeImage(string imageFilePath, string imageFilePathOutput, int newWidth, int maxImageFileSize)
{
    using (Image myImage = Image.FromFile(imageFilePath))
    {
        Size newSize = myImage.Size;
        if (newSize.Width > newWidth)
            newSize = Resize(newSize, newWidth);

        using (Image myResizedImage = new Bitmap(myImage, newSize))
        {
            EncoderParameters eps = null;
            ImageCodecInfo ici = null;
            string fileExt = System.IO.Path.GetExtension(imageFilePath).ToLower();
            switch (fileExt)
            {
                case ".jpg":
                    eps = new System.Drawing.Imaging.EncoderParameters(1);
                    ici = GetEncoderInfo(ImageFormat.Jpeg);
                    break;
                default:
                    throw new NotImplementedException("Image format not supported");
            }

            // Starting quality
            long qualityValue = 90;
            long lastSize = 0;
            while (true)
            {
                eps.Param[0] = new System.Drawing.Imaging.EncoderParameter(System.Drawing.Imaging.Encoder.Quality, qualityValue);

                using (System.IO.MemoryStream ms = new System.IO.MemoryStream())
                {
                    myResizedImage.Save(ms, ici, eps);

                    if (ms.Length <= maxImageFileSize || (lastSize > 0 && lastSize <= ms.Length))
                    {
                        // Write new image file.
                        System.IO.File.WriteAllBytes(imageFilePathOutput, ms.ToArray());
                        return;
                    }
                    lastSize = ms.Length;
                }

                // Decrease quality
                qualityValue -= 5;
            }
        }
    }
}

private static Size Resize(Size size, int newWidth)
{
    float factor = (float)size.Height / size.Width;
    return new Size(newWidth, Convert.ToInt32(newWidth * factor));
}

private static ImageCodecInfo GetEncoderInfo(ImageFormat format)
{
    return ImageCodecInfo.GetImageEncoders().FirstOrDefault(x => x.FormatID == format.Guid);
}

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Carlos Villegas

I forgot to mention that you will require these namespaces:
System.Drawing
System.Drawing.Imaging

canuckconsulting

ASKER

This is perfect; thanks! Can you advis if it is possible to convert the contents of ms back into an Image? I would like the method to return the reduced image which will be saved later on?

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Carlos Villegas

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canuckconsulting

ASKER

Perfect...thank you!

Carlos Villegas

Glad to help!