我理解使用
BitmapFactory
可以将文件转换为位图,但是否有办法将位图图像转换为文件呢?希望这可以帮到你:
//create a file to write bitmap data
File f = new File(context.getCacheDir(), filename);
f.createNewFile();
//Convert bitmap to byte array
Bitmap bitmap = your bitmap;
ByteArrayOutputStream bos = new ByteArrayOutputStream();
bitmap.compress(CompressFormat.PNG, 0 /*ignored for PNG*/, bos);
byte[] bitmapdata = bos.toByteArray();
//write the bytes in file
FileOutputStream fos = new FileOutputStream(f);
fos.write(bitmapdata);
fos.flush();
fos.close();
File file = new File("path");
OutputStream os = new BufferedOutputStream(new FileOutputStream(file));
bitmap.compress(Bitmap.CompressFormat.JPEG, 100, os);
os.close();
File()
构造函数。 - fraggjkee将 Bitmap
转换为 File
需要在后台进行 (不要在主线程中进行),否则会导致界面卡顿,特别是当 bitmap
很大时。
File file;
public class fileFromBitmap extends AsyncTask<Void, Integer, String> {
Context context;
Bitmap bitmap;
String path_external = Environment.getExternalStorageDirectory() + File.separator + "temporary_file.jpg";
public fileFromBitmap(Bitmap bitmap, Context context) {
this.bitmap = bitmap;
this.context= context;
}
@Override
protected void onPreExecute() {
super.onPreExecute();
// before executing doInBackground
// update your UI
// exp; make progressbar visible
}
@Override
protected String doInBackground(Void... params) {
ByteArrayOutputStream bytes = new ByteArrayOutputStream();
bitmap.compress(Bitmap.CompressFormat.JPEG, 100, bytes);
file = new File(Environment.getExternalStorageDirectory() + File.separator + "temporary_file.jpg");
try {
FileOutputStream fo = new FileOutputStream(file);
fo.write(bytes.toByteArray());
fo.flush();
fo.close();
} catch (IOException e) {
e.printStackTrace();
}
return null;
}
@Override
protected void onPostExecute(String s) {
super.onPostExecute(s);
// back to main thread after finishing doInBackground
// update your UI or take action after
// exp; make progressbar gone
sendFile(file);
}
}
称之为
new fileFromBitmap(my_bitmap, getApplicationContext()).execute();
你必须在onPostExecute
中使用file
。
要更改存储在缓存中的file
的目录,请替换以下行:
file = new File(Environment.getExternalStorageDirectory() + File.separator + "temporary_file.jpg");
使用:
file = new File(context.getCacheDir(), "temporary_file.jpg");
大多数答案过长或过短,无法实现目的。对于那些正在寻找将位图转换为文件对象的Java或Kotlin代码的人来说,这里有一篇我写的详细文章。在Android中将位图转换为文件
public static File bitmapToFile(Context context,Bitmap bitmap, String fileNameToSave) { // File name like "image.png"
//create a file to write bitmap data
File file = null;
try {
file = new File(Environment.getExternalStorageDirectory() + File.separator + fileNameToSave);
file.createNewFile();
//Convert bitmap to byte array
ByteArrayOutputStream bos = new ByteArrayOutputStream();
bitmap.compress(Bitmap.CompressFormat.PNG, 0 , bos); // YOU can also save it in JPEG
byte[] bitmapdata = bos.toByteArray();
//write the bytes in file
FileOutputStream fos = new FileOutputStream(file);
fos.write(bitmapdata);
fos.flush();
fos.close();
return file;
}catch (Exception e){
e.printStackTrace();
return file; // it will return null
}
}
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
setContentView(R.layout.activity_main)
// Get the bitmap from assets and display into image view
val bitmap = assetsToBitmap("tulip.jpg")
// If bitmap is not null
bitmap?.let {
image_view_bitmap.setImageBitmap(bitmap)
}
// Click listener for button widget
button.setOnClickListener{
if(bitmap!=null){
// Save the bitmap to a file and display it into image view
val uri = bitmapToFile(bitmap)
image_view_file.setImageURI(uri)
// Display the saved bitmap's uri in text view
text_view.text = uri.toString()
// Show a toast message
toast("Bitmap saved in a file.")
}else{
toast("bitmap not found.")
}
}
}
// Method to get a bitmap from assets
private fun assetsToBitmap(fileName:String):Bitmap?{
return try{
val stream = assets.open(fileName)
BitmapFactory.decodeStream(stream)
}catch (e:IOException){
e.printStackTrace()
null
}
}
// Method to save an bitmap to a file
private fun bitmapToFile(bitmap:Bitmap): Uri {
// Get the context wrapper
val wrapper = ContextWrapper(applicationContext)
// Initialize a new file instance to save bitmap object
var file = wrapper.getDir("Images",Context.MODE_PRIVATE)
file = File(file,"${UUID.randomUUID()}.jpg")
try{
// Compress the bitmap and save in jpg format
val stream:OutputStream = FileOutputStream(file)
bitmap.compress(Bitmap.CompressFormat.JPEG,100,stream)
stream.flush()
stream.close()
}catch (e:IOException){
e.printStackTrace()
}
// Return the saved bitmap uri
return Uri.parse(file.absolutePath)
}
}
ByteArrayOutputStream
,从中获取一个字节数组,然后将该数组写入到FileOutputStream
中?为什么不直接在Bitmap.compress
中使用FileOutputStream
呢? - InsanityOnABun