[英]How to resize BitmapImage using Writeable Bitmap Extension
我正在使用WriteableBitmap扩展名, 可用于与BitMapImage相关的操作。我正在开发Windows Phone 8和8.1应用程序,试图从Zipfile加载一些图像。 加载图片时,我需要根据设备的屏幕尺寸调整图片大小。
注意:
我正在开发一个支持WPF的跨平台移动应用程序,Windows Phone 8,Windows Phone 8.1。我使用以下代码在WPF中实现了相同的senario。
private Bitmap LoadAndResizeBitmap()
{
Bitmap bitmap = (Bitmap)Bitmap.FromStream(fileEntry.OpenEntryStream());
if (bitmap.Height > _primaryscreenHeight)
{
System.Drawing.Size oldSize = new System.Drawing.Size(bitmap.Width, bitmap.Height);
System.Drawing.Size newSize = GetNewImageSize(oldSize);
Bitmap newImage = ResizeImage(bitmap, newSize);
bitmap = newImage;
}
return bitmap;
}
/// <summary>
/// <summary>
/// Resize the Image
/// </summary>
/// <param name="image"></param>
/// <param name="newSize"></param>
/// <returns></returns>
private Bitmap ResizeImage(Image image, System.Drawing.Size newSize)
{
// Make a rectangle that is the new size
Rectangle destRect = new Rectangle(0, 0, newSize.Width, newSize.Height);
// Make a bitmap that is the new size
Bitmap destImage = new Bitmap(newSize.Width, newSize.Height);
// Set new image to the resolution of the original
destImage.SetResolution(image.HorizontalResolution, image.VerticalResolution);
// Create a GDI holder and use it
using (Graphics graphics = Graphics.FromImage(destImage))
{
// Set our quality options
graphics.CompositingMode = CompositingMode.SourceCopy;
graphics.CompositingQuality = CompositingQuality.HighQuality;
graphics.InterpolationMode = InterpolationMode.HighQualityBicubic;
graphics.SmoothingMode = SmoothingMode.HighQuality;
graphics.PixelOffsetMode = PixelOffsetMode.HighQuality;
// Resize original image into new one
using (var wrapMode = new ImageAttributes())
{
wrapMode.SetWrapMode(WrapMode.TileFlipXY);
graphics.DrawImage(image, destRect, 0, 0, image.Width, image.Height, GraphicsUnit.Pixel, wrapMode);
}
}
return destImage;
}
/// <summary>
/// Get new Image Size
/// </summary>
/// <param name="oldSize"></param>
/// <returns></returns>
private System.Drawing.Size GetNewImageSize(System.Drawing.Size oldSize)
{
float ratio;
if (oldSize.Height > oldSize.Width)
{
ratio = (float) oldSize.Width/oldSize.Height;
}
else
{
ratio = (float) oldSize.Height/oldSize.Width;
}
int newWidth = (int) (_maxImageHeight*ratio);
System.Drawing.Size newSize = new System.Drawing.Size(newWidth, _maxImageHeight);
return newSize;
}
由于没有系统,我无法在Windows Hone 8或8.1中使用相同的实现。在这些平台中绘制。因此我选择了WritableBitmap扩展。它还支持Win 8,win Phone 8,8.1和WPF
过去这对我有用。 您主要感兴趣的是解码像素的宽度和高度。 ps此代码成功将byte [](数据库友好)转换为BitmapImage:
using(MemoryStream strmImg = new MemoryStream(profileImage.Image))
{
BitmapImage myBitmapImage = new BitmapImage();
myBitmapImage.BeginInit();
myBitmapImage.CacheOption = BitmapCacheOption.OnLoad;
myBitmapImage.StreamSource = strmImg;
myBitmapImage.DecodePixelWidth = 200;
myBitmapImage.DecodePixelHeight= 250;
myBitmapImage.EndInit();
EmployeeProfileImage = myBitmapImage;
}
我希望这有帮助,
罗卡
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