Reducing image dimension increases the file size C#

Question

I am trying to resize image, my current image dimensions are (1800*1197) and having file size = 305kb, when i tried to reduce dimensions to (1200*900) and save the file its size drastically increases to 1.75mb.

I have called the below method resizeImage like:

Image MainImage = resizeImage(BaseImage, 1200, 900, false);

I am using the function to resize image as below:

public static Bitmap resizeImage(Image imgToResize, int lnWidth, int lnHeight, bool _FixHeightWidth)
    {
        System.Drawing.Bitmap bmpOut = null;
        Graphics g;
        try
        {
            Bitmap loBMP = new Bitmap(imgToResize);
            ImageFormat loFormat = loBMP.RawFormat;

            decimal lnRatio;
            int lnNewWidth = 0;
            int lnNewHeight = 0;

            //*** If the image is smaller than a thumbnail just return it

            if (loBMP.Width < lnWidth && loBMP.Height < lnHeight && _FixHeightWidth == false)
            {
                bmpOut = new Bitmap(loBMP.Width, loBMP.Height);
                g = Graphics.FromImage(bmpOut);

                g.InterpolationMode = System.Drawing.Drawing2D.InterpolationMode.HighQualityBilinear;
                g.FillRectangle(Brushes.White, 0, 0, loBMP.Width, loBMP.Height);
                g.DrawImage(loBMP, 0, 0, loBMP.Width, loBMP.Height);
                loBMP.Dispose();
                return bmpOut;
            }

            if (loBMP.Width > loBMP.Height)
            {
                lnRatio = (decimal)lnWidth / loBMP.Width;
                lnNewWidth = lnWidth;
                decimal lnTemp = loBMP.Height * lnRatio;
                lnNewHeight = (int)lnTemp;
            }
            else
            {
                lnRatio = (decimal)lnHeight / loBMP.Height;
                lnNewHeight = lnHeight;
                decimal lnTemp = loBMP.Width * lnRatio;
                lnNewWidth = (int)lnTemp;
            }

            if (_FixHeightWidth == true)
            {
                lnNewHeight = lnHeight;
                lnNewWidth = lnWidth;
            }

            bmpOut = new Bitmap(lnNewWidth, lnNewHeight);
            g = Graphics.FromImage(bmpOut);
            g.InterpolationMode = System.Drawing.Drawing2D.InterpolationMode.HighQualityBilinear;
            g.FillRectangle(Brushes.White, 0, 0, lnNewWidth, lnNewHeight);
            g.DrawImage(loBMP, 0, 0, lnNewWidth, lnNewHeight);
            loBMP.Dispose();
        }
        catch
        {
            return null;
        }
        return bmpOut;
    }

After this conversion success i simply save the file, but instead of decreasing, it increases file size. so i just wanted the file size either should remain same(305kb) or reduce it accordingly.

Note: I just want suggestions on how to work with this kind of situation, also some explanation would be great that what thing is causing this issue, also if any other solutions are there.

Sample image:

Update: File format is '.jpg'

MainImage.Save(Path.Combine(pathForSaving, fileName));

What file format is the input and output image *files*? Jpeg? Bmp? Png? — Lasse V. Karlsen, Nov 23 '16 at 10:49
bmp != bmp . Look up on bitmap compression and you will see that there are many ways to store an image as a bitmap(same applies to jpg). For better compression i would suggest using png.(or jpg for photos). — sknt, Nov 23 '16 at 10:59
@LasseV.Karlsen `MainImage.Save(Path.Combine(pathForSaving, fileName));` — Harsh Vyas, Nov 23 '16 at 11:01
You can and probably should set the [quality parameter](http://stackoverflow.com/questions/1484759/quality-of-a-saved-jpg-in-c-sharp) for the jpeg file! — TaW, Nov 23 '16 at 11:04
@HarshVyas And that's the problem. That statement will likely save as PNG file format, even though the extension may be .JPG on the filename. You need to specify the jpeg file format to get a *real* .jpg file. See https://msdn.microsoft.com/en-us/library/ktx83wah(v=vs.110).aspx for more information. — Lasse V. Karlsen, Nov 23 '16 at 11:35
@LasseV.Karlsen Ok read the link, quite helpful, as per now i have tried to implement encoder parameter, i think this will work perfectly for me. lets hope :) — Harsh Vyas, Nov 23 '16 at 11:45

score 1 · Accepted Answer · answered Nov 23 '16 at 11:19

I supose you are using an original ImageFormat of file to write the new image... If the original image is a bitmap, the result format will be to, only change the extension... You need to set an Encoder. Also, you can try to change the IterpolationMode to a medium-low quality or the format of the file to PNG format is better for internet use...

Reducing image dimension increases the file size C#

1 Answers1