Do you have a fast method of resizing a System.Drawing.Image object?
Preferably one that results in a quality image. I have a method found on
codeproject.com, but as noted in the comment, it requires a lot of cpu time.
int y = (int)(((double)((double)m_nWidth/(double)m_Image.Size.Width)) *
(double)m_Image.Size.Height);
thumb = Resize(new Bitmap(m_Image), m_nWidth, y, (bool)(m_nWidth > 200));
public static Bitmap Resize(Bitmap b, int nWidth, int nHeight, bool
bBilinear)
{
//Bitmap bTemp = (Bitmap)b.Clone();
Bitmap bTemp = b;
b = new Bitmap(nWidth, nHeight, bTemp.PixelFormat);
double nXFactor = (double)bTemp.Width/(double)nWidth;
double nYFactor = (double)bTemp.Height/(double)nHeight;
if (bBilinear)
{
double fraction_x, fraction_y, one_minus_x, one_minus_y;
int ceil_x, ceil_y, floor_x, floor_y;
Color c1 = new Color();
Color c2 = new Color();
Color c3 = new Color();
Color c4 = new Color();
byte red, green, blue;
byte b1, b2;
for (int x = 0; x < b.Width; ++x)
{
for (int y = 0; y < b.Height; ++y)
{
// Setup
floor_x = (int)Math.Floor(x * nXFactor);
floor_y = (int)Math.Floor(y * nYFactor);
ceil_x = floor_x + 1;
if (ceil_x >= bTemp.Width) ceil_x = floor_x;
ceil_y = floor_y + 1;
if (ceil_y >= bTemp.Height) ceil_y = floor_y;
fraction_x = x * nXFactor - floor_x;
fraction_y = y * nYFactor - floor_y;
one_minus_x = 1.0 - fraction_x;
one_minus_y = 1.0 - fraction_y;
c1 = bTemp.GetPixel(floor_x, floor_y);
c2 = bTemp.GetPixel(ceil_x, floor_y);
c3 = bTemp.GetPixel(floor_x, ceil_y);
c4 = bTemp.GetPixel(ceil_x, ceil_y);
// Blue
b1 = (byte)(one_minus_x * c1.B + fraction_x * c2.B);
b2 = (byte)(one_minus_x * c3.B + fraction_x * c4.B);
blue = (byte)(one_minus_y * (double)(b1) + fraction_y * (double)(b2));
// Green
b1 = (byte)(one_minus_x * c1.G + fraction_x * c2.G);
b2 = (byte)(one_minus_x * c3.G + fraction_x * c4.G);
green = (byte)(one_minus_y * (double)(b1) + fraction_y * (double)(b2));
// Red
b1 = (byte)(one_minus_x * c1.R + fraction_x * c2.R);
b2 = (byte)(one_minus_x * c3.R + fraction_x * c4.R);
red = (byte)(one_minus_y * (double)(b1) + fraction_y * (double)(b2));
b.SetPixel(x,y, System.Drawing.Color.FromArgb(255, red, green, blue));
}
}
}
else
{
for (int x = 0; x < b.Width; ++x)
for (int y = 0; y < b.Height; ++y)
b.SetPixel(x, y, bTemp.GetPixel((int)(Math.Floor(x * nXFactor)),
(int)(Math.Floor(y * nYFactor))));
}
return b;
}
"Shiv Kumar" <sh***@erolsnoooospaaaam.com> wrote in message
news:Ow**************@TK2MSFTNGP11.phx.gbl...
David,
For now I will assume you know the basic mechanics of the http protocol
and how browsers work with regards to <img>, <link>, <script> tags etc.
So in theory, your image control's ImageUrl should point to (to keep it
simple) an aspx page whose sole purpose is:
Given the url to the full sized image (as a parameter), to return the
thumbnail of that image. Better still, an additional parameter in the url
will tell it if you need a thumbnail or full size.
So lets say that the ImageUrl property of the image control would look
like this:
/ImageProcessor.aspx?filename=someimage.jpg&size=sm all
No in the ImageProcessor.aspx you simply load up the actual file and (if
the size parameter = small) get a thumbnail.
The way you return the "image" (binary) to the browser is by writing to
the Response.OutputStream
A simple method like this should help
"stream" in this case Response.OutputStream. In my case width, height and
img are private members of my class that were initialized at the time of
creating and instance.
public void GetThumbnail(ref System.IO.Stream stream)
{
System.Drawing.Image thumbnail;
System.IntPtr ptr = new IntPtr();
/* If the width parameter is "0", assume normal image size */
if (width != 0)
{
thumbnail = img.GetThumbnailImage(width, height, null, ptr);
thumbnail.Save(stream, img.RawFormat);
thumbnail.Dispose();
}
else
{
img.Save(stream, img.RawFormat);
}
img.Dispose();
}
--
Shiv R. Kumar
http://www.matlus.com
"David W. Simmonds" <da***@simmonds.ca> wrote in message
news:5jeOb.149615$ts4.20420@pd7tw3no... I have a DataList control that has an Image control in the ItemTemplate.
I would like to resize the image that goes into that control. I have a
series of jpg files that are full size, full resolution (ie. large). I have a
database that contains references to the pictures. Currently I have to
resize the jpgs manually, and then point the ImageUrl property at that
jpg using databinding. This works fine. I would like to avoid the resizing
step and have the server code do it. I could then have the full image load
into another browser window if the user requests it, but the initial image
would be a realistic size (640x480 or 720x480). Is there a way to replace the
Image control in the datalist with a new resized one?
If I had a Button object in the datalist ItemTemplate, how do I receive
the event that it has been pressed? With just a button on the form, I can
just dblclick the control in the IDE and the event is added to the code.
