我正在研究从web服务器下载图像的功能,在屏幕上显示它,如果用户希望保持图像,将其保存在SD卡的某个文件夹中。有没有一种简单的方法来获取位图并将其保存到我选择的SD卡文件夹中?
我的问题是,我可以下载图像,在屏幕上显示为位图。我能够找到的将图像保存到特定文件夹的唯一方法是使用FileOutputStream,但这需要一个字节数组。我不知道如何转换(如果这是正确的方式)从位图到字节数组,所以我可以使用FileOutputStream写入数据。
我的另一个选择是使用MediaStore:
MediaStore.Images.Media.insertImage(getContentResolver(), bm,
barcodeNumber + ".jpg Card Image", barcodeNumber + ".jpg Card Image");
它可以很好地保存到SD卡,但不允许您自定义文件夹。
我发现发送PNG和透明度的方式。
String file_path = Environment.getExternalStorageDirectory().getAbsolutePath() +
"/CustomDir";
File dir = new File(file_path);
if(!dir.exists())
dir.mkdirs();
String format = new SimpleDateFormat("yyyyMMddHHmmss",
java.util.Locale.getDefault()).format(new Date());
File file = new File(dir, format + ".png");
FileOutputStream fOut;
try {
fOut = new FileOutputStream(file);
yourbitmap.compress(Bitmap.CompressFormat.PNG, 85, fOut);
fOut.flush();
fOut.close();
} catch (Exception e) {
e.printStackTrace();
}
Uri uri = Uri.fromFile(file);
Intent intent = new Intent(android.content.Intent.ACTION_SEND);
intent.setType("image/*");
intent.putExtra(android.content.Intent.EXTRA_SUBJECT, "");
intent.putExtra(android.content.Intent.EXTRA_TEXT, "");
intent.putExtra(Intent.EXTRA_STREAM, uri);
startActivity(Intent.createChooser(intent,"Sharing something")));
为视频创建一个视频缩略图。如果视频损坏或格式不支持,它可能返回null。
private void makeVideoPreview() {
Bitmap thumbnail = ThumbnailUtils.createVideoThumbnail(videoAbsolutePath, MediaStore.Images.Thumbnails.MINI_KIND);
saveImage(thumbnail);
}
使用以下代码将位图保存在sdcard中
商店形象
private void storeImage(Bitmap image) {
File pictureFile = getOutputMediaFile();
if (pictureFile == null) {
Log.d(TAG,
"Error creating media file, check storage permissions: ");// e.getMessage());
return;
}
try {
FileOutputStream fos = new FileOutputStream(pictureFile);
image.compress(Bitmap.CompressFormat.PNG, 90, fos);
fos.close();
} catch (FileNotFoundException e) {
Log.d(TAG, "File not found: " + e.getMessage());
} catch (IOException e) {
Log.d(TAG, "Error accessing file: " + e.getMessage());
}
}
获取图像存储路径
/** Create a File for saving an image or video */
private File getOutputMediaFile(){
// To be safe, you should check that the SDCard is mounted
// using Environment.getExternalStorageState() before doing this.
File mediaStorageDir = new File(Environment.getExternalStorageDirectory()
+ "/Android/data/"
+ getApplicationContext().getPackageName()
+ "/Files");
// This location works best if you want the created images to be shared
// between applications and persist after your app has been uninstalled.
// Create the storage directory if it does not exist
if (! mediaStorageDir.exists()){
if (! mediaStorageDir.mkdirs()){
return null;
}
}
// Create a media file name
String timeStamp = new SimpleDateFormat("ddMMyyyy_HHmm").format(new Date());
File mediaFile;
String mImageName="MI_"+ timeStamp +".jpg";
mediaFile = new File(mediaStorageDir.getPath() + File.separator + mImageName);
return mediaFile;
}
我还想保存一张图片。但是我的问题(?)是我想从我画的位图中保存它。
我是这样写的:
@Override
public boolean onOptionsItemSelected(MenuItem item) {
switch (item.getItemId()) {
case R.id.save_sign:
myView.save();
break;
}
return false;
}
public void save() {
String filename;
Date date = new Date(0);
SimpleDateFormat sdf = new SimpleDateFormat ("yyyyMMddHHmmss");
filename = sdf.format(date);
try{
String path = Environment.getExternalStorageDirectory().toString();
OutputStream fOut = null;
File file = new File(path, "/DCIM/Signatures/"+filename+".jpg");
fOut = new FileOutputStream(file);
mBitmap.compress(Bitmap.CompressFormat.JPEG, 85, fOut);
fOut.flush();
fOut.close();
MediaStore.Images.Media.insertImage(getContentResolver()
,file.getAbsolutePath(),file.getName(),file.getName());
}catch (Exception e) {
e.printStackTrace();
}
}
您想要保存位图到您选择的目录。我做了一个ImageWorker库,使用户能够加载,保存和转换位图/绘图/base64图像。
最小SDK - 14
先决条件
保存文件需要WRITE_EXTERNAL_STORAGE权限。
检索文件需要READ_EXTERNAL_STORAGE权限。
储蓄位图/ Drawable Base64
ImageWorker.to(context).
directory("ImageWorker").
subDirectory("SubDirectory").
setFileName("Image").
withExtension(Extension.PNG).
save(sourceBitmap,85)
加载位图
val bitmap: Bitmap? = ImageWorker.from(context).
directory("ImageWorker").
subDirectory("SubDirectory").
setFileName("Image").
withExtension(Extension.PNG).
load()
实现
添加依赖关系
在项目级别Gradle
allprojects {
repositories {
...
maven { url 'https://jitpack.io' }
}
}
在应用级Gradle
dependencies {
implementation 'com.github.ihimanshurawat:ImageWorker:0.51'
}
你可以在https://github.com/ihimanshurawat/ImageWorker/blob/master/README.md上阅读更多
您应该使用Bitmap.compress()方法将位图保存为文件。它将压缩(如果所使用的格式允许的话)您的图片并将其推入OutputStream。
下面是一个通过getImageBitmap(myurl)获得的位图实例,可以压缩为JPEG,压缩率为85%:
// Assume block needs to be inside a Try/Catch block.
String path = Environment.getExternalStorageDirectory().toString();
OutputStream fOut = null;
Integer counter = 0;
File file = new File(path, "FitnessGirl"+counter+".jpg"); // the File to save , append increasing numeric counter to prevent files from getting overwritten.
fOut = new FileOutputStream(file);
Bitmap pictureBitmap = getImageBitmap(myurl); // obtaining the Bitmap
pictureBitmap.compress(Bitmap.CompressFormat.JPEG, 85, fOut); // saving the Bitmap to a file compressed as a JPEG with 85% compression rate
fOut.flush(); // Not really required
fOut.close(); // do not forget to close the stream
MediaStore.Images.Media.insertImage(getContentResolver(),file.getAbsolutePath(),file.getName(),file.getName());