如何压缩图像,但不调整它使用Xamarin Android
本文关键字:调整 Android Xamarin 何压缩 压缩 图像 | 更新日期: 2023-09-27 17:50:59
我从服务器得到一个图像,这是相当大的15MB左右,但我想保持宽高比,但压缩文件的大小,因为我正在加载多个文件,大约相同的大小?这些图像被下载为bitmap,并使用SetImageBitmap来显示图像
您可以通过将图像转换为jpeg或png来实现这一点。这是位图到PNG转换例程的快速而粗糙的实现:
public string ResizeImage(string sourceFilePath)
{
Android.Graphics.Bitmap bmp = Android.Graphics.BitmapFactory.DecodeFile (sourceFilePath);
string newPath = sourceFilePath.Replace(".bmp", ".png");
using (var fs = new FileStream (newPath, FileMode.OpenOrCreate)) {
bmp.Compress (Android.Graphics.Bitmap.CompressFormat.Png, 100, fs);
}
return newPath;
}
它对文件扩展名做了假设,但可以很容易地修改。
下面是我用来验证压缩的完整示例:
public class MainActivity : Activity
{
public const string BITMAP_URL = @"http://www.openjpeg.org/samples/Bretagne2.bmp";
public string ResizeImage(string sourceFilePath)
{
Android.Graphics.Bitmap bmp = Android.Graphics.BitmapFactory.DecodeFile (sourceFilePath);
string newPath = sourceFilePath.Replace(".bmp", ".png");
using (var fs = new FileStream (newPath, FileMode.OpenOrCreate)) {
bmp.Compress (Android.Graphics.Bitmap.CompressFormat.Png, 100, fs);
}
return newPath;
}
protected override void OnCreate (Bundle bundle)
{
base.OnCreate (bundle);
SetContentView (Resource.Layout.Main);
Button button = FindViewById<Button> (Resource.Id.myButton);
button.Click += delegate {
System.Threading.Tasks.Task.Run( () => {
RunOnUiThread( () => Toast.MakeText(this, "Downloading file", ToastLength.Long).Show());
string downloadFile = DownloadSourceImage(BITMAP_URL);
RunOnUiThread( () => Toast.MakeText(this, "Rescaling image: " + downloadFile, ToastLength.Long).Show());
string convertedFile = ResizeImage(downloadFile);
var bmpFileSize = (new FileInfo(downloadFile)).Length;
var pngFileSize = (new FileInfo(convertedFile)).Length;
RunOnUiThread( () => Toast.MakeText(this, "BMP is " + bmpFileSize + "B. PNG is " + pngFileSize + "B.", ToastLength.Long).Show());
});
};
}
public string DownloadSourceImage(string url)
{
System.Net.WebClient client = new System.Net.WebClient ();
string fileName = url.Split ('/').LastOrDefault ();
string downloadedFilePath = Path.Combine(Android.OS.Environment.ExternalStorageDirectory.AbsolutePath, fileName);
if (File.Exists (downloadedFilePath) == false) {
client.DownloadFile (url, downloadedFilePath);
}
return downloadedFilePath;
}
}
您可以使用其他文件格式压缩图像(例如:jpeg)。或者您可以在保持宽高比的同时调整图像的大小。