Resizing an image in asp.net without losing the image quality
I am developing an ASP.NET 3.5 web application in which I am allowing my users to upload either jpeg,gif,bmp or png images. If the uploaded image dimensions are greater then 103 x 32 the I want to resize the uploaded image to 103 x 32. I have read some blog posts and articles, and have also tried some of the code samples but nothing seems to work right. Has anyone succeed in doing this?
Solution 1:
This is the code I use. It supports rotation, and also sets the image resolution to the JPEG standards of 72dpi@24-bit color (by default GDI+ saves images at 96dpi@32-bit color). It also fixes the black/gray border problem that some people experience when resizing images.
/// <summary>
/// Resizes and rotates an image, keeping the original aspect ratio. Does not dispose the original
/// Image instance.
/// </summary>
/// <param name="image">Image instance</param>
/// <param name="width">desired width</param>
/// <param name="height">desired height</param>
/// <param name="rotateFlipType">desired RotateFlipType</param>
/// <returns>new resized/rotated Image instance</returns>
public static Image Resize(Image image, int width, int height, RotateFlipType rotateFlipType)
{
// clone the Image instance, since we don't want to resize the original Image instance
var rotatedImage = image.Clone() as Image;
rotatedImage.RotateFlip(rotateFlipType);
var newSize = CalculateResizedDimensions(rotatedImage, width, height);
var resizedImage = new Bitmap(newSize.Width, newSize.Height, PixelFormat.Format32bppArgb);
resizedImage.SetResolution(72, 72);
using (var graphics = Graphics.FromImage(resizedImage))
{
// set parameters to create a high-quality thumbnail
graphics.InterpolationMode = InterpolationMode.HighQualityBicubic;
graphics.SmoothingMode = SmoothingMode.AntiAlias;
graphics.CompositingQuality = CompositingQuality.HighQuality;
graphics.PixelOffsetMode = PixelOffsetMode.HighQuality;
// use an image attribute in order to remove the black/gray border around image after resize
// (most obvious on white images), see this post for more information:
// http://www.codeproject.com/KB/GDI-plus/imgresizoutperfgdiplus.aspx
using (var attribute = new ImageAttributes())
{
attribute.SetWrapMode(WrapMode.TileFlipXY);
// draws the resized image to the bitmap
graphics.DrawImage(rotatedImage, new Rectangle(new Point(0, 0), newSize), 0, 0, rotatedImage.Width, rotatedImage.Height, GraphicsUnit.Pixel, attribute);
}
}
return resizedImage;
}
/// <summary>
/// Calculates resized dimensions for an image, preserving the aspect ratio.
/// </summary>
/// <param name="image">Image instance</param>
/// <param name="desiredWidth">desired width</param>
/// <param name="desiredHeight">desired height</param>
/// <returns>Size instance with the resized dimensions</returns>
private static Size CalculateResizedDimensions(Image image, int desiredWidth, int desiredHeight)
{
var widthScale = (double)desiredWidth / image.Width;
var heightScale = (double)desiredHeight / image.Height;
// scale to whichever ratio is smaller, this works for both scaling up and scaling down
var scale = widthScale < heightScale ? widthScale : heightScale;
return new Size
{
Width = (int) (scale * image.Width),
Height = (int) (scale * image.Height)
};
}
Solution 2:
I had the same problem a while back and dealt with it this way:
private Image RezizeImage(Image img, int maxWidth, int maxHeight)
{
if(img.Height < maxHeight && img.Width < maxWidth) return img;
using (img)
{
Double xRatio = (double)img.Width / maxWidth;
Double yRatio = (double)img.Height / maxHeight;
Double ratio = Math.Max(xRatio, yRatio);
int nnx = (int)Math.Floor(img.Width / ratio);
int nny = (int)Math.Floor(img.Height / ratio);
Bitmap cpy = new Bitmap(nnx, nny, PixelFormat.Format32bppArgb);
using (Graphics gr = Graphics.FromImage(cpy))
{
gr.Clear(Color.Transparent);
// This is said to give best quality when resizing images
gr.InterpolationMode = InterpolationMode.HighQualityBicubic;
gr.DrawImage(img,
new Rectangle(0, 0, nnx, nny),
new Rectangle(0, 0, img.Width, img.Height),
GraphicsUnit.Pixel);
}
return cpy;
}
}
private MemoryStream BytearrayToStream(byte[] arr)
{
return new MemoryStream(arr, 0, arr.Length);
}
private void HandleImageUpload(byte[] binaryImage)
{
Image img = RezizeImage(Image.FromStream(BytearrayToStream(binaryImage)), 103, 32);
img.Save("IMAGELOCATION.png", System.Drawing.Imaging.ImageFormat.Gif);
}
I just read that this was the the way to get highest quality.
Solution 3:
The code associated with the actual resizing of the bitmap is as follows.
public static Bitmap ResizeBitmap( Bitmap originalBitmap, int requiredHeight, int requiredWidth )
{
int[] heightWidthRequiredDimensions;
// Pass dimensions to worker method depending on image type required
heightWidthRequiredDimensions = WorkDimensions(originalBitmap.Height, originalBitmap.Width, requiredHeight, requiredWidth);
Bitmap resizedBitmap = new Bitmap( heightWidthRequiredDimensions[1],
heightWidthRequiredDimensions[0] );
const float resolution = 72;
resizedBitmap.SetResolution( resolution, resolution );
Graphics graphic = Graphics.FromImage( (Image) resizedBitmap );
graphic.InterpolationMode = System.Drawing.Drawing2D.InterpolationMode.HighQualityBicubic;
graphic.DrawImage( originalBitmap, 0, 0, resizedBitmap.Width, resizedBitmap.Height );
graphic.Dispose();
originalBitmap.Dispose();
//resizedBitmap.Dispose(); // Still in use
return resizedBitmap;
}
private static int[] WorkDimensions(int originalHeight, int originalWidth, int requiredHeight, int requiredWidth )
{
int imgHeight = 0;
int imgWidth = 0;
imgWidth = requiredHeight;
imgHeight = requiredWidth;
int requiredHeightLocal = originalHeight;
int requiredWidthLocal = originalWidth;
double ratio = 0;
// Check height first
// If original height exceeds maximum, get new height and work ratio.
if ( originalHeight > imgHeight )
{
ratio = double.Parse( ( (double) imgHeight / (double) originalHeight ).ToString() );
requiredHeightLocal = imgHeight;
requiredWidthLocal = (int) ( (decimal) originalWidth * (decimal) ratio );
}
// Check width second. It will most likely have been sized down enough
// in the previous if statement. If not, change both dimensions here by width.
// If new width exceeds maximum, get new width and height ratio.
if ( requiredWidthLocal >= imgWidth )
{
ratio = double.Parse( ( (double) imgWidth / (double) originalWidth ).ToString() );
requiredWidthLocal = imgWidth;
requiredHeightLocal = (int) ( (double) originalHeight * (double) ratio );
}
int[] heightWidthDimensionArr = { requiredHeightLocal, requiredWidthLocal };
return heightWidthDimensionArr;
}
}
This blog post contains full source code for image resizing, and compression (if required)
http://blog.bombdefused.com/2010/08/bulk-image-optimizer-in-c-full-source.html