许多应用程序允许共享图片,这些图片是从图库中挑选出来的。
他们上传原始图像文件了吗?大概是1-3mb?或者他们会处理吗?
在任何情况下,我如何从文件路径中获取图像,通过降低分辨率来减小其大小,并将其保存在其他位置,然后尝试上载?
我尝试过的:
Bitmap photo = decodeSampledBitmapFromFile(filePath, DESIRED_WIDTH,
DESIRED_HEIGHT);
FileOutputStream out = new FileOutputStream(filePath);
photo.compress(Bitmap.CompressFormat.JPEG, 100, out);
public static Bitmap decodeSampledBitmapFromFile(String path, int reqWidth,
int reqHeight) {
final BitmapFactory.Options options = new BitmapFactory.Options();
options.inJustDecodeBounds = true;
BitmapFactory.decodeFile(path, options);
final int height = options.outHeight;
final int width = options.outWidth;
options.inPreferredConfig = Bitmap.Config.ARGB_8888;
int inSampleSize = 1;
if (height > reqHeight) {
inSampleSize = Math.round((float) height / (float) reqHeight);
}
int expectedWidth = width / inSampleSize;
if (expectedWidth > reqWidth) {
inSampleSize = Math.round((float) width / (float) reqWidth);
}
options.inSampleSize = inSampleSize;
options.inJustDecodeBounds = false;
return BitmapFactory.decodeFile(path, options);
}
但这是他们正确的做法吗?因为我看到的答案是compression operation takes rather big amount of time
here
发布于 2015-08-31 19:10:57
我在上传之前使用这个函数来减小图片的大小,它将图片大小减小到接近200KB,并且保持了相对较好的质量,你可以通过改变REQUIRED_SIZE和inSampleSize来修改它来满足你的目的:
public File saveBitmapToFile(File file){
try {
// BitmapFactory options to downsize the image
BitmapFactory.Options o = new BitmapFactory.Options();
o.inJustDecodeBounds = true;
o.inSampleSize = 6;
// factor of downsizing the image
FileInputStream inputStream = new FileInputStream(file);
//Bitmap selectedBitmap = null;
BitmapFactory.decodeStream(inputStream, null, o);
inputStream.close();
// The new size we want to scale to
final int REQUIRED_SIZE=75;
// Find the correct scale value. It should be the power of 2.
int scale = 1;
while(o.outWidth / scale / 2 >= REQUIRED_SIZE &&
o.outHeight / scale / 2 >= REQUIRED_SIZE) {
scale *= 2;
}
BitmapFactory.Options o2 = new BitmapFactory.Options();
o2.inSampleSize = scale;
inputStream = new FileInputStream(file);
Bitmap selectedBitmap = BitmapFactory.decodeStream(inputStream, null, o2);
inputStream.close();
// here i override the original image file
file.createNewFile();
FileOutputStream outputStream = new FileOutputStream(file);
selectedBitmap.compress(Bitmap.CompressFormat.JPEG, 100 , outputStream);
return file;
} catch (Exception e) {
return null;
}
}
注意:我在这个函数中调整和覆盖了原始文件的图像,你也可以把它写到另一个文件中。
我希望它能帮助你。
发布于 2013-09-02 21:10:19
这很有效,试试这个吧
private String decodeFile(String path,int DESIREDWIDTH, int DESIREDHEIGHT) {
String strMyImagePath = null;
Bitmap scaledBitmap = null;
try {
// Part 1: Decode image
Bitmap unscaledBitmap = ScalingUtilities.decodeFile(path, DESIREDWIDTH, DESIREDHEIGHT, ScalingLogic.FIT);
if (!(unscaledBitmap.getWidth() <= DESIREDWIDTH && unscaledBitmap.getHeight() <= DESIREDHEIGHT)) {
// Part 2: Scale image
scaledBitmap = ScalingUtilities.createScaledBitmap(unscaledBitmap, DESIREDWIDTH, DESIREDHEIGHT, ScalingLogic.FIT);
} else {
unscaledBitmap.recycle();
return path;
}
// Store to tmp file
String extr = Environment.getExternalStorageDirectory().toString();
File mFolder = new File(extr + "/TMMFOLDER");
if (!mFolder.exists()) {
mFolder.mkdir();
}
String s = "tmp.png";
File f = new File(mFolder.getAbsolutePath(), s);
strMyImagePath = f.getAbsolutePath();
FileOutputStream fos = null;
try {
fos = new FileOutputStream(f);
scaledBitmap.compress(Bitmap.CompressFormat.JPEG, 75, fos);
fos.flush();
fos.close();
} catch (FileNotFoundException e) {
e.printStackTrace();
} catch (Exception e) {
e.printStackTrace();
}
scaledBitmap.recycle();
} catch (Throwable e) {
}
if (strMyImagePath == null) {
return path;
}
return strMyImagePath;
}
ScalingUtilities.java
import android.content.res.Resources;
import android.graphics.Bitmap;
import android.graphics.Bitmap.Config;
import android.graphics.BitmapFactory;
import android.graphics.BitmapFactory.Options;
import android.graphics.Canvas;
import android.graphics.Paint;
import android.graphics.Rect;
/**
* Class containing static utility methods for bitmap decoding and scaling
*
* @author
*/
public class ScalingUtilities {
/**
* Utility function for decoding an image resource. The decoded bitmap will
* be optimized for further scaling to the requested destination dimensions
* and scaling logic.
*
* @param res The resources object containing the image data
* @param resId The resource id of the image data
* @param dstWidth Width of destination area
* @param dstHeight Height of destination area
* @param scalingLogic Logic to use to avoid image stretching
* @return Decoded bitmap
*/
public static Bitmap decodeResource(Resources res, int resId, int dstWidth, int dstHeight,
ScalingLogic scalingLogic) {
Options options = new Options();
options.inJustDecodeBounds = true;
BitmapFactory.decodeResource(res, resId, options);
options.inJustDecodeBounds = false;
options.inSampleSize = calculateSampleSize(options.outWidth, options.outHeight, dstWidth,
dstHeight, scalingLogic);
Bitmap unscaledBitmap = BitmapFactory.decodeResource(res, resId, options);
return unscaledBitmap;
}
public static Bitmap decodeFile(String path, int dstWidth, int dstHeight,
ScalingLogic scalingLogic) {
Options options = new Options();
options.inJustDecodeBounds = true;
BitmapFactory.decodeFile(path, options);
options.inJustDecodeBounds = false;
options.inSampleSize = calculateSampleSize(options.outWidth, options.outHeight, dstWidth,
dstHeight, scalingLogic);
Bitmap unscaledBitmap = BitmapFactory.decodeFile(path, options);
return unscaledBitmap;
}
/**
* Utility function for creating a scaled version of an existing bitmap
*
* @param unscaledBitmap Bitmap to scale
* @param dstWidth Wanted width of destination bitmap
* @param dstHeight Wanted height of destination bitmap
* @param scalingLogic Logic to use to avoid image stretching
* @return New scaled bitmap object
*/
public static Bitmap createScaledBitmap(Bitmap unscaledBitmap, int dstWidth, int dstHeight,
ScalingLogic scalingLogic) {
Rect srcRect = calculateSrcRect(unscaledBitmap.getWidth(), unscaledBitmap.getHeight(),
dstWidth, dstHeight, scalingLogic);
Rect dstRect = calculateDstRect(unscaledBitmap.getWidth(), unscaledBitmap.getHeight(),
dstWidth, dstHeight, scalingLogic);
Bitmap scaledBitmap = Bitmap.createBitmap(dstRect.width(), dstRect.height(),
Config.ARGB_8888);
Canvas canvas = new Canvas(scaledBitmap);
canvas.drawBitmap(unscaledBitmap, srcRect, dstRect, new Paint(Paint.FILTER_BITMAP_FLAG));
return scaledBitmap;
}
/**
* ScalingLogic defines how scaling should be carried out if source and
* destination image has different aspect ratio.
*
* CROP: Scales the image the minimum amount while making sure that at least
* one of the two dimensions fit inside the requested destination area.
* Parts of the source image will be cropped to realize this.
*
* FIT: Scales the image the minimum amount while making sure both
* dimensions fit inside the requested destination area. The resulting
* destination dimensions might be adjusted to a smaller size than
* requested.
*/
public static enum ScalingLogic {
CROP, FIT
}
/**
* Calculate optimal down-sampling factor given the dimensions of a source
* image, the dimensions of a destination area and a scaling logic.
*
* @param srcWidth Width of source image
* @param srcHeight Height of source image
* @param dstWidth Width of destination area
* @param dstHeight Height of destination area
* @param scalingLogic Logic to use to avoid image stretching
* @return Optimal down scaling sample size for decoding
*/
public static int calculateSampleSize(int srcWidth, int srcHeight, int dstWidth, int dstHeight,
ScalingLogic scalingLogic) {
if (scalingLogic == ScalingLogic.FIT) {
final float srcAspect = (float)srcWidth / (float)srcHeight;
final float dstAspect = (float)dstWidth / (float)dstHeight;
if (srcAspect > dstAspect) {
return srcWidth / dstWidth;
} else {
return srcHeight / dstHeight;
}
} else {
final float srcAspect = (float)srcWidth / (float)srcHeight;
final float dstAspect = (float)dstWidth / (float)dstHeight;
if (srcAspect > dstAspect) {
return srcHeight / dstHeight;
} else {
return srcWidth / dstWidth;
}
}
}
/**
* Calculates source rectangle for scaling bitmap
*
* @param srcWidth Width of source image
* @param srcHeight Height of source image
* @param dstWidth Width of destination area
* @param dstHeight Height of destination area
* @param scalingLogic Logic to use to avoid image stretching
* @return Optimal source rectangle
*/
public static Rect calculateSrcRect(int srcWidth, int srcHeight, int dstWidth, int dstHeight,
ScalingLogic scalingLogic) {
if (scalingLogic == ScalingLogic.CROP) {
final float srcAspect = (float)srcWidth / (float)srcHeight;
final float dstAspect = (float)dstWidth / (float)dstHeight;
if (srcAspect > dstAspect) {
final int srcRectWidth = (int)(srcHeight * dstAspect);
final int srcRectLeft = (srcWidth - srcRectWidth) / 2;
return new Rect(srcRectLeft, 0, srcRectLeft + srcRectWidth, srcHeight);
} else {
final int srcRectHeight = (int)(srcWidth / dstAspect);
final int scrRectTop = (int)(srcHeight - srcRectHeight) / 2;
return new Rect(0, scrRectTop, srcWidth, scrRectTop + srcRectHeight);
}
} else {
return new Rect(0, 0, srcWidth, srcHeight);
}
}
/**
* Calculates destination rectangle for scaling bitmap
*
* @param srcWidth Width of source image
* @param srcHeight Height of source image
* @param dstWidth Width of destination area
* @param dstHeight Height of destination area
* @param scalingLogic Logic to use to avoid image stretching
* @return Optimal destination rectangle
*/
public static Rect calculateDstRect(int srcWidth, int srcHeight, int dstWidth, int dstHeight,
ScalingLogic scalingLogic) {
if (scalingLogic == ScalingLogic.FIT) {
final float srcAspect = (float)srcWidth / (float)srcHeight;
final float dstAspect = (float)dstWidth / (float)dstHeight;
if (srcAspect > dstAspect) {
return new Rect(0, 0, dstWidth, (int)(dstWidth / srcAspect));
} else {
return new Rect(0, 0, (int)(dstHeight * srcAspect), dstHeight);
}
} else {
return new Rect(0, 0, dstWidth, dstHeight);
}
}
}
发布于 2019-06-26 04:17:58
这是一个在内存中处理的解决方案,不需要在文件系统上实际生成文件。
从一些片段中,在用户选择了一个图像文件之后:
@Override
public void onActivityResult(int requestCode, int resultCode, Intent imageReturnedIntent) {
super.onActivityResult(requestCode, resultCode, imageReturnedIntent);
if (imageReturnedIntent == null
|| imageReturnedIntent.getData() == null) {
return;
}
// aiming for ~500kb max. assumes typical device image size is around 2megs
int scaleDivider = 4;
try {
// 1. Convert uri to bitmap
Uri imageUri = imageReturnedIntent.getData();
Bitmap fullBitmap = MediaStore.Images.Media.getBitmap(getActivity().getContentResolver(), imageUri);
// 2. Get the downsized image content as a byte[]
int scaleWidth = fullBitmap.getWidth() / scaleDivider;
int scaleHeight = fullBitmap.getHeight() / scaleDivider;
byte[] downsizedImageBytes =
getDownsizedImageBytes(fullBitmap, scaleWidth, scaleHeight);
// 3. Upload the byte[]; Eg, if you are using Firebase
StorageReference storageReference =
FirebaseStorage.getInstance().getReference("/somepath");
storageReference.putBytes(downsizedImageBytes);
}
catch (IOException ioEx) {
ioEx.printStackTrace();
}
}
public byte[] getDownsizedImageBytes(Bitmap fullBitmap, int scaleWidth, int scaleHeight) throws IOException {
Bitmap scaledBitmap = Bitmap.createScaledBitmap(fullBitmap, scaleWidth, scaleHeight, true);
// 2. Instantiate the downsized image content as a byte[]
ByteArrayOutputStream baos = new ByteArrayOutputStream();
scaledBitmap.compress(Bitmap.CompressFormat.JPEG, 100, baos);
byte[] downsizedImageBytes = baos.toByteArray();
return downsizedImageBytes;
}
感谢:
将uri转换为位图:https://stackoverflow.com/a/4717740/2162226
https://stackoverflow.com/questions/18573774
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