public virtual Image GetThumbnail()
{
// Flag whether a new image is required
bool recalculate = false;
double newWidth = Width;
double newHeight = Height;
// Is there a cached source image available? If not,
// load the image if a filename was specified; otherwise
// use the image in the Image property
if (!IsSameSrcImage(mCache)) {
if (mImagePath.Length > 0) {
// Load via stream rather than Image.FromFile to release the file
// handle immediately
if (mSrcImage != null)
mSrcImage.Dispose();
// Wrap the FileStream in a "using" directive, to ensure the handle
// gets closed when the object goes out of scope
using (Stream stream = new FileStream(mImagePath, FileMode.Open))
mSrcImage = Image.FromStream(stream);
recalculate = true;
}
}
// Check whether the required destination image properties have
// changed
if (!IsSameDstImage(mCache)) {
// Yes, so we need to recalculate.
// If you opted to specify width and height as percentages of the original
// image's width and height, compute these now
if (UsePercentages) {
if (Width != 0) {
newWidth = mSrcImage.Width * Width / 100;
if (PreserveAspectRatio) {
newHeight = newWidth * mSrcImage.Height / mSrcImage.Width;
}
}
if (Height != 0) {
newHeight = mSrcImage.Height * Height / 100;
if (PreserveAspectRatio) {
newWidth = newHeight * mSrcImage.Width / mSrcImage.Height;
}
}
} else {
// If you specified an aspect ratio and absolute width or height, then calculate this
// now; if you accidentally specified both a width and height, ignore the
// PreserveAspectRatio flag
if (PreserveAspectRatio) {
if (Width != 0 && Height == 0) {
newHeight = (Width / mSrcImage.Width) * mSrcImage.Height;
} else if (Height != 0 && Width == 0) {
newWidth = (Height / mSrcImage.Height) * mSrcImage.Width;
}
}
}
recalculate = true;
}
if (recalculate) {
// Calculate the new image
if (mDstImage != null) {
mDstImage.Dispose();
mGraphics.Dispose();
}
Bitmap bitmap = new Bitmap((int)newWidth, (int)newHeight, mSrcImage.PixelFormat);
mGraphics = Graphics.FromImage(bitmap);
mGraphics.SmoothingMode = System.Drawing.Drawing2D.SmoothingMode.HighQuality;
mGraphics.InterpolationMode = System.Drawing.Drawing2D.InterpolationMode.HighQualityBicubic;
mGraphics.DrawImage(mSrcImage, 0, 0, bitmap.Width, bitmap.Height);
mDstImage = bitmap;
// Cache the image and its associated settings
mCache = MemberwiseClone() as ImageResizer;
}
return mDstImage;
}
protected virtual bool IsSameDstImage(ImageResizer other)
{
if (other != null) {
return (Width == other.Width
&& Height == other.Height
&& UsePercentages == other.UsePercentages
&& PreserveAspectRatio == other.PreserveAspectRatio);
}
return false;
}
protected virtual bool IsSameSrcImage(ImageResizer other)
{
if (other != null) {
return (File == other.File
&& Image == other.Image);
}
return false;
}
public ImageHelper(Stream stream)
{
resizer = new ImageResizer() {
Image = Image.FromStream(stream),
};
}