I'm trying to rescale uploaded jpeg in asp.net
So I go:
Image original = Image.FromStream(myPostedFile.InputStream);
int w=original.Width, h=original.Height;
using(Graphics g = Graphics.FromImage(original))
{
g.ScaleTransform(0.5f, 0.5f); ... // e.g.
using (Bitmap done = new Bitmap(w, h, g))
{
done.Save( Server.MapPath(saveas), ImageFormat.Jpeg );
//saves blank black, though with correct width and height
}
}
this saves a virgin black jpeg whatever file i give it.
Though if i take input image stream immediately into done
bitmap, it does recompress and save it fine, like:
Image original = Image.FromStream(myPostedFile.InputStream);
using (Bitmap done = new Bitmap(original))
{
done.Save( Server.MapPath(saveas), ImageFormat.Jpeg );
}
Do i have to make some magic with g?
upd: i tried:
Image original = Image.FromStream(fstream);
int w=original.Width, h=original.Height;
using(Bitmap b = new Bitmap(original)) //also tried new Bitmap(w,h)
using (Graphics g = Graphics.FromImage(b))
{
g.DrawImage(original, 0, 0, w, h); //also tried g.DrawImage(b, 0, 0, w, h)
using (Bitmap done = new Bitmap(w, h, g))
{
done.Save( Server.MapPath(saveas), ImageFormat.Jpeg );
}
}
same story - pure black of correct dimensions
Since you didn't fill the area with background of image you're reading from inputStream,you can only get a blank image that way.
Instead of using scaling the image,you can use Fill background into a resized area.
Check this out:
Image img = Image.FromFile(Server.MapPath("a.png"));
int w = img.Width;
int h = img.Height;
//Create an empty bitmap with scaled size,here half
Bitmap bmp = new Bitmap(w / 2, h / 2);
//Create graphics object to draw
Graphics g = Graphics.FromImage(bmp);
//You can also use SmoothingMode,CompositingMode and CompositingQuality
//of Graphics object to preserve saving options for new image.
//Create drawing area with a rectangle
Rectangle drect = new Rectangle(0, 0, bmp.Width, bmp.Height);
//Draw image into your rectangle area
g.DrawImage(img, drect);
//Save your new image
bmp.Save(Server.MapPath("a2.jpg"), ImageFormat.Jpeg);
Hope this helps
Myra
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