Upload og skalering af billede med .net

Det kommer helt an på hvordan din skalering laves. Hvis du bruger GetThumbnailImage vil du ofte få denne fejl. Det skyldes at den tager et indlejret Thumbnail som ligger i billedet.

Det er GetThumbnailImage jeg benytter. Er der andre bedre muligheder?

Jeg har engang downloadet et eksempel til skalering af billeder, jeg kan desværre ikke huske hvor jeg downloade det - men her er koden. Jeg har selv brugt koden med succes :-)

using System;
using System.Drawing;
using System.Drawing.Imaging;
using System.Drawing.Drawing2D;

namespace Tutorial
{
    class ImageResize
    {
        enum Dimensions
        {
            Width,
            Height
        }
        enum AnchorPosition
        {
            Top,
            Center,
            Bottom,
            Left,
            Right
        }
        [STAThread]
        static void Main(string[] args)
        {
            //set a working directory
            string WorkingDirectory = @"C:\Projects\Tutorials\ImageResize";

            //create a image object containing a verticel photograph
            Image imgPhotoVert = Image.FromFile(WorkingDirectory + @"\imageresize_vert.jpg");
            Image imgPhotoHoriz = Image.FromFile(WorkingDirectory + @"\imageresize_horiz.jpg");
            Image imgPhoto = null;

            imgPhoto = ScaleByPercent(imgPhotoVert, 50);
            imgPhoto.Save(WorkingDirectory + @"\images\imageresize_1.jpg", ImageFormat.Jpeg);
            imgPhoto.Dispose();

            imgPhoto = ConstrainProportions(imgPhotoVert, 200, Dimensions.Width);
            imgPhoto.Save(WorkingDirectory + @"\images\imageresize_2.jpg", ImageFormat.Jpeg);
            imgPhoto.Dispose();

            imgPhoto = FixedSize(imgPhotoVert, 200, 200);
            imgPhoto.Save(WorkingDirectory + @"\images\imageresize_3.jpg", ImageFormat.Jpeg);
            imgPhoto.Dispose();

            imgPhoto = Crop(imgPhotoVert, 200, 200, AnchorPosition.Center);
            imgPhoto.Save(WorkingDirectory + @"\images\imageresize_4.jpg", ImageFormat.Jpeg);
            imgPhoto.Dispose();

            imgPhoto = Crop(imgPhotoHoriz, 200, 200, AnchorPosition.Center);
            imgPhoto.Save(WorkingDirectory + @"\images\imageresize_5.jpg", ImageFormat.Jpeg);
            imgPhoto.Dispose();

        }
        static Image ScaleByPercent(Image imgPhoto, int Percent)
        {
            float nPercent = ((float)Percent/100);

            int sourceWidth = imgPhoto.Width;
            int sourceHeight = imgPhoto.Height;
            int sourceX = 0;
            int sourceY = 0;

            int destX = 0;
            int destY = 0;
            int destWidth  = (int)(sourceWidth * nPercent);
            int destHeight = (int)(sourceHeight * nPercent);

            Bitmap bmPhoto = new Bitmap(destWidth, destHeight, PixelFormat.Format24bppRgb);
            bmPhoto.SetResolution(imgPhoto.HorizontalResolution, imgPhoto.VerticalResolution);

            Graphics grPhoto = Graphics.FromImage(bmPhoto);
            grPhoto.InterpolationMode = InterpolationMode.HighQualityBicubic;

            grPhoto.DrawImage(imgPhoto,
                new Rectangle(destX,destY,destWidth,destHeight),
                new Rectangle(sourceX,sourceY,sourceWidth,sourceHeight),
                GraphicsUnit.Pixel);

            grPhoto.Dispose();
            return bmPhoto;
        }
        static Image ConstrainProportions(Image imgPhoto, int Size, Dimensions Dimension)
        {
            int sourceWidth = imgPhoto.Width;
            int sourceHeight = imgPhoto.Height;
            int sourceX = 0;
            int sourceY = 0;
            int destX = 0;
            int destY = 0;
            float nPercent = 0;

            switch(Dimension)
            {
                case Dimensions.Width:
                    nPercent = ((float)Size/(float)sourceWidth);
                    break;
                default:
                    nPercent = ((float)Size/(float)sourceHeight);
                    break;
            }
               
            int destWidth  = (int)(sourceWidth * nPercent);
            int destHeight = (int)(sourceHeight * nPercent);

            Bitmap bmPhoto = new Bitmap(destWidth, destHeight, PixelFormat.Format24bppRgb);
            bmPhoto.SetResolution(imgPhoto.HorizontalResolution, imgPhoto.VerticalResolution);

            Graphics grPhoto = Graphics.FromImage(bmPhoto);
            grPhoto.InterpolationMode = InterpolationMode.HighQualityBicubic;

            grPhoto.DrawImage(imgPhoto,
            new Rectangle(destX,destY,destWidth,destHeight),
            new Rectangle(sourceX,sourceY,sourceWidth,sourceHeight),
            GraphicsUnit.Pixel);

            grPhoto.Dispose();
            return bmPhoto;
        }

        static Image FixedSize(Image imgPhoto, int Width, int Height)
        {
            int sourceWidth = imgPhoto.Width;
            int sourceHeight = imgPhoto.Height;
            int sourceX = 0;
            int sourceY = 0;
            int destX = 0;
            int destY = 0;

            float nPercent = 0;
            float nPercentW = 0;
            float nPercentH = 0;

            nPercentW = ((float)Width/(float)sourceWidth);
            nPercentH = ((float)Height/(float)sourceHeight);

            //if we have to pad the height pad both the top and the bottom
            //with the difference between the scaled height and the desired height
            if(nPercentH < nPercentW)
            {
                nPercent = nPercentH;
                destX = (int)((Width - (sourceWidth * nPercent))/2);
            }
            else
            {
                nPercent = nPercentW;
                destY = (int)((Height - (sourceHeight * nPercent))/2);
            }
       
            int destWidth  = (int)(sourceWidth * nPercent);
            int destHeight = (int)(sourceHeight * nPercent);

            Bitmap bmPhoto = new Bitmap(Width, Height, PixelFormat.Format24bppRgb);
            bmPhoto.SetResolution(imgPhoto.HorizontalResolution, imgPhoto.VerticalResolution);

            Graphics grPhoto = Graphics.FromImage(bmPhoto);
            grPhoto.Clear(Color.Red);
            grPhoto.InterpolationMode = InterpolationMode.HighQualityBicubic;

            grPhoto.DrawImage(imgPhoto,
                new Rectangle(destX,destY,destWidth,destHeight),
                new Rectangle(sourceX,sourceY,sourceWidth,sourceHeight),
                GraphicsUnit.Pixel);

            grPhoto.Dispose();
            return bmPhoto;
        }
        static Image Crop(Image imgPhoto, int Width, int Height, AnchorPosition Anchor)
        {
            int sourceWidth = imgPhoto.Width;
            int sourceHeight = imgPhoto.Height;
            int sourceX = 0;
            int sourceY = 0;
            int destX = 0;
            int destY = 0;

            float nPercent = 0;
            float nPercentW = 0;
            float nPercentH = 0;

            nPercentW = ((float)Width/(float)sourceWidth);
            nPercentH = ((float)Height/(float)sourceHeight);

            if(nPercentH < nPercentW)
            {
                nPercent = nPercentW;
                switch(Anchor)
                {
                    case AnchorPosition.Top:
                        destY = 0;
                        break;
                    case AnchorPosition.Bottom:
                        destY = (int)(Height - (sourceHeight * nPercent));
                        break;
                    default:
                        destY = (int)((Height - (sourceHeight * nPercent))/2);
                        break;
                }               
            }
            else
            {
                nPercent = nPercentH;
                switch(Anchor)
                {
                    case AnchorPosition.Left:
                        destX = 0;
                        break;
                    case AnchorPosition.Right:
                        destX = (int)(Width - (sourceWidth * nPercent));
                        break;
                    default:
                        destX = (int)((Width - (sourceWidth * nPercent))/2);
                        break;
                }           
            }

            int destWidth  = (int)(sourceWidth * nPercent);
            int destHeight = (int)(sourceHeight * nPercent);

            Bitmap bmPhoto = new Bitmap(Width, Height, PixelFormat.Format24bppRgb);
            bmPhoto.SetResolution(imgPhoto.HorizontalResolution, imgPhoto.VerticalResolution);

            Graphics grPhoto = Graphics.FromImage(bmPhoto);
            grPhoto.InterpolationMode = InterpolationMode.HighQualityBicubic;

            grPhoto.DrawImage(imgPhoto,
                new Rectangle(destX,destY,destWidth,destHeight),
                new Rectangle(sourceX,sourceY,sourceWidth,sourceHeight),
                GraphicsUnit.Pixel);

            grPhoto.Dispose();
            return bmPhoto;
        }
    }
}


/Askhoej

Brug denne her til at skalere med:

static Image Crop(Image imgPhoto, int Width, int Height, AnchorPosition Anchor)

takker for det hurtige og brugbare svar. Jeg benytter godtnok vb, men efter en mindre omskrivning virker det fint.

Hvordan kan man få System.Drawing.Image konverteret til System.Web.UI.WebControls.Image?

clausjul>> eeeh... det gør man ikke... System.Web.UI.WebControls.Image svarer til en <img src=""> som html

Det jeg ville gøre er at skalere billedet før det kommer ud på websiden. Derfor skal billedet egentlig være af type System.Web.UI.WebControls.Image..

clausjul>> for fanden... System.Web.UI.WebControls.Image er ikke noget billede !!

du skal istedet henvise til din aspx-side som laver billedet:

<img src="resize.aspx?image=hej.jpg" />

OK! Jeg var bare lidt forvirret over System.Drawing.Image og System.Web.UI.WebControls.Image - men nu har jeg fast grund under fødderne ;-)

det er måske heller ikke det smarteste at klasserne hedder det samme :/

en tommelfingerregel er, at klasserne i webcontrols-namespacet producerer almindelig HTML/Javasscript-kode når siden bliver sendt til klienten, så hvis det du har gang i ikke kan lade sig gøre på en .html-side, så kan de klasser ikke hjælpe dig.

pointen: du kan ikke skalere et billede (ikke på pixel-niveau i hvert fald) på en html-side