In my android application i am using whatsapp like image compression and after that i convert the compressed image bitmap to string using Base64 encoding,what i noticed is that when i compress a 5mb image and save it in another locations its just of 60kb or 70kb something like that and the Base64 encoded string is taking 500kb or 600kb for the same image, why its like that? Is there any way to convert the compressed image to string with its same size.Below is my code.
Bitmap bitmapImg;
if (requestCode == FILE_SELECT_CODE) {
if(data!= null) {
try {
Uri selectedImageUri = data.getData();
String mimeType = getContentResolver().getType(selectedImageUri);
compressImage(selectedImageUri);
// Converting compressed bitmap to string
ByteArrayOutputStream byteArrayOS = new ByteArrayOutputStream();
bitmapImg.compress(Bitmap.CompressFormat.PNG, 100, byteArrayOS);
String strBitmap = Base64.encodeToString(byteArrayOS.toByteArray(), Base64.DEFAULT);
} catch (Exception e) {
e.printStackTrace();
}
}
}
private String compressImage(Uri selImageUri) {
String fileStrName = null;
bitmapImg = null;
try {
String filePath = getRealPathFromURI(selImageUri);
BitmapFactory.Options options = new BitmapFactory.Options();
// by setting this field as true, the actual bitmap pixels are not loaded in the memory. Just the bounds are loaded. If
// you try the use the bitmap here, you will get null.
options.inJustDecodeBounds = true;
Bitmap bmpTemp = BitmapFactory.decodeFile(filePath, options);
int actualHeight = options.outHeight;
int actualWidth = options.outWidth;
// max Height and width values of the compressed image is taken as 816x612
float maxHeight = 816.0f;
float maxWidth = 612.0f;
float imgRatio = actualWidth / actualHeight;
float maxRatio = maxWidth / maxHeight;
// width and height values are set maintaining the aspect ratio of the image
if (actualHeight > maxHeight || actualWidth > maxWidth) {
if (imgRatio < maxRatio) {
imgRatio = maxHeight / actualHeight;
actualWidth = (int) (imgRatio * actualWidth);
actualHeight = (int) maxHeight;
} else if (imgRatio > maxRatio) {
imgRatio = maxWidth / actualWidth;
actualHeight = (int) (imgRatio * actualHeight);
actualWidth = (int) maxWidth;
} else {
actualHeight = (int) maxHeight;
actualWidth = (int) maxWidth;
}
}
// setting inSampleSize value allows to load a scaled down version of the original image
options.inSampleSize = calculateInSampleSize(options, actualWidth, actualHeight);
// inJustDecodeBounds set to false to load the actual bitmap
options.inJustDecodeBounds = false;
// this options allow android to claim the bitmap memory if it runs low on memory
options.inPurgeable = true;
options.inInputShareable = true;
options.inTempStorage = new byte[16 * 1024];
try {
// load the bitmap from its path
bmpTemp = BitmapFactory.decodeFile(filePath, options);
} catch (OutOfMemoryError exception) {
exception.printStackTrace();
}
try {
bitmapImg = Bitmap.createBitmap(actualWidth, actualHeight, Bitmap.Config.ARGB_8888);
} catch (OutOfMemoryError exception) {
exception.printStackTrace();
}
float ratioX = actualWidth / (float) options.outWidth;
float ratioY = actualHeight / (float) options.outHeight;
float middleX = actualWidth / 2.0f;
float middleY = actualHeight / 2.0f;
Matrix scaleMatrix = new Matrix();
scaleMatrix.setScale(ratioX, ratioY, middleX, middleY);
Canvas canvas = new Canvas(bitmapImg);
canvas.setMatrix(scaleMatrix);
canvas.drawBitmap(bmpTemp, middleX - bmpTemp.getWidth() / 2, middleY - bmpTemp.getHeight() / 2, new Paint(Paint.FILTER_BITMAP_FLAG));
// check the rotation of the image and display it properly
ExifInterface exif;
try {
exif = new ExifInterface(filePath);
int orientation = exif.getAttributeInt(ExifInterface.TAG_ORIENTATION, 0);
Matrix matrix = new Matrix();
if (orientation == 6) {
matrix.postRotate(90);
} else if (orientation == 3) {
matrix.postRotate(180);
} else if (orientation == 8) {
matrix.postRotate(270);
}
bitmapImg = Bitmap.createBitmap(bitmapImg, 0, 0, bitmapImg.getWidth(), bitmapImg.getHeight(), matrix, true);
} catch (IOException e) {
e.printStackTrace();
}
FileOutputStream out = null;
String filename = getFilename();
try {
out = new FileOutputStream(filename);
// write the compressed bitmap at the destination specified by filename.
bitmapImg.compress(Bitmap.CompressFormat.JPEG, 80, out);
} catch (FileNotFoundException e) {
e.printStackTrace();
}
} catch (Exception e) {
e.printStackTrace();
}
return fileStrName;
}
public int calculateInSampleSize(BitmapFactory.Options options, int reqWidth, int reqHeight) {
final int height = options.outHeight;
final int width = options.outWidth;
int inSampleSize = 1;
if (height > reqHeight || width > reqWidth) {
final int heightRatio = Math.round((float) height/ (float) reqHeight);
final int widthRatio = Math.round((float) width / (float) reqWidth);
inSampleSize = heightRatio < widthRatio ? heightRatio : widthRatio;
}
final float totalPixels = width * height;
final float totalReqPixelsCap = reqWidth * reqHeight * 2;
while (totalPixels / (inSampleSize * inSampleSize) > totalReqPixelsCap) {
inSampleSize++;
}
return inSampleSize;
}
private String getRealPathFromURI(Uri contentUri) {
Cursor cursor = getContentResolver().query(contentUri, null, null, null, null);
if (cursor == null) {
return contentUri.getPath();
} else {
cursor.moveToFirst();
int index = cursor.getColumnIndex(MediaStore.Images.ImageColumns.DATA);
return cursor.getString(index);
}
}
public String getFilename() {
File file = new File(Environment.getExternalStorageDirectory().getPath(), "MyFolder/Images");
if (!file.exists()) {
file.mkdirs();
}
String uriSting = (file.getAbsolutePath() + "/" + System.currentTimeMillis() + ".jpg");
return uriSting;
}
Here the compressed image is of size 60kb or 70kb but when I save the strBitmap to database its taking 500kb or 600kb.How can i convert the compressed bitmap with the same size to string.
There's one big difference in your images though.
The image you store as a file is stored as a JPEG
bitmapImg.compress(Bitmap.CompressFormat.JPEG, 80, out);
while the Base64 encoded string is a PNG
bitmapImg.compress(Bitmap.CompressFormat.PNG, 100, byteArrayOS);
This can explain the size differences. Another thing could be, that bitmapImg changed it's contents inbetween both compressions as well.
来源：https://stackoverflow.com/questions/43487288/android-how-to-convert-the-compressed-images-to-string-with-minimum-size