Question

I am trying to save an image from string.

so I want to know how I can set image height and width in inches at the time of saving the image.

my code follows for image saving :

 private void Base64ToImage(string base64String)
    {
        Image fullSizeImg = null;
        byte[] imageBytes = Convert.FromBase64String(base64String);
        MemoryStream ms = new MemoryStream(imageBytes);
        fullSizeImg = Image.FromStream(ms, true);
        System.Drawing.Image.GetThumbnailImageAbort dummyCallBack = new System.Drawing.Image.GetThumbnailImageAbort(ThumbnailCallback);
        System.Drawing.Image thumbNailImg = fullSizeImg.GetThumbnailImage(700, 800, dummyCallBack, IntPtr.Zero);
        thumbNailImg.Save(ImagePath, System.Drawing.Imaging.ImageFormat.Png);
        fullSizeImg.Dispose();
        thumbNailImg.Dispose();


    }

Answer 1

Bitmaps don’t have a size in inches, their size is measured in pixels. That said most modern bitmat formats have a piece of metadata called DPI (dots per inch) that is used to translate a size in pixels to a size in inches via the simple formula:

inches = pixels / dpi

For the Image class you set metadata using the SetPropertyItem Method where the pieces of metadata we are interested in are:

• PropertyTagResolutionUnit – set this to “2” for inches
• PropertyTagXResolution – Essentially the X DPI as long as PropertyTagResolutionUnit is in inches.
• PropertyTagYResolution – The Y DPI as long as PropertyTagResolutionUnit is in inches

See Property Item Descriptions for details.

(Actually, I realised half way through writing this that the setting of property metadata using SetPropertyItem looks really complicated – you might just be better off using Bitmat instead, which has resolution properties making the whole thing a lot easier)