Android-缩放、旋转位图并将其保存到SD卡，而不会丢失质量

Question

我正在做一个应用程序，用相机拍照，然后旋转和缩放。我需要旋转图像，因为相机返回错误的旋转图像，我需要缩放它以减小其大小。我首先将相机返回的原始图像保存在临时目录中，然后读取并进行修改，将新图像保存到新文件中。我尝试使用矩阵来旋转和缩放图片，但它失去了质量。然后我试着先用位图来缩放它。创建缩放位图，然后使用矩阵旋转，但结果比仅使用矩阵的结果更糟糕。然后我尝试先旋转它，然后使用“始终位图”调整大小。创建缩放位图。图像不会丢失质量，但在旋转后，当我缩放图像时，图像会被拉伸，宽度和高度会反转。还尝试根据所做的旋转反转高度和宽度，但再次失去质量。这是我写的最后一段代码：

in= new FileInputStream(tempDir+"/"+photo1_path);
            out = new FileOutputStream(file+"/picture.png");
            Bitmap src = BitmapFactory.decodeStream(in);
            int iwidth = src.getWidth();
            int iheight = src.getHeight();
            int newWidth = 0;
            int newHeight = 0;

                newWidth = 800;
                newHeight = 600;

              // calculate the scale - in this case = 0.4f
              float scaleWidth = ((float) newWidth) / iwidth;
              float scaleHeight = ((float) newHeight) / iheight;

              // createa matrix for the manipulation
              Matrix matrix = new Matrix();
              // resize the bit map
              //matrix.postScale(scaleWidth, scaleHeight);
              int orientation = getOrientation(MyActivity.this,Uri.parse(tempDir+"/"+photo1_path));
              switch(orientation) {
                case 3:
                    orientation = 180;
                    break;
                case 6:
                    orientation = 90;
                   break;
                case 8:
                    orientation = 270;
                    break;
              }
              int rotate = 0;
              switch(orientation) {
                case 90:
                    rotate=90;
                    break;
                case 180:
                    rotate=180;
                    break;
                case 270:
                    rotate=270;
                    break;

              }
              // rotate the Bitmap
              matrix.postRotate(rotate);

              src =Bitmap.createScaledBitmap(src , newWidth, newHeight, false);
              // recreate the new Bitmap
              Bitmap new_bit = Bitmap.createBitmap(src, 0, 0,
                                src.getWidth(), src.getHeight(), matrix, true);
                      new_bit.compress(Bitmap.CompressFormat.PNG, 100, out);

有什么建议吗？

编辑：如果我只旋转或只缩放图像，它不会失去质量。当我两者都做时，图像会失去质量。此外，如果我在调整图像大小并缩放后将其放入ImageView中，它不会丢失质量，只是当我将其保存到文件时会丢失质量。

Answer 1

不要让新位图只是覆盖

int角=0； int值角=0；位图位图；

        @Override
        public void onClick(View v) {

            System.out.println("valueeeeeee  " + angle);
            if (bitmap != null) {

                angle = valueangle + 90;



                Matrix matrix = new Matrix();
                matrix.postRotate(angle);

                bitmap = Bitmap.createBitmap(
                        bitmap , 0, 0,
                        bitmap .getWidth(),
                        bitmap .getHeight(), matrix, true);



                main_img.setImageBitmap(bitmap );

            } else {

                System.out.println(" bitmap is null");
            }

        }

Answer 2

使用此方法旋转位图。。。

private Bitmap checkifImageRotated() {
    ExifInterface exif;
    try {
        exif = new ExifInterface(file.getAbsolutePath());
        int orientation = exif.getAttributeInt(ExifInterface.TAG_ORIENTATION, ExifInterface.ORIENTATION_NORMAL);
        int rotate = 0;
        switch (orientation) {
            case ExifInterface.ORIENTATION_ROTATE_270 :
                rotate = -90;
                break;
            case ExifInterface.ORIENTATION_ROTATE_180 :
                rotate = 180;
                break;
            case ExifInterface.ORIENTATION_ROTATE_90 :
                rotate = 90;
                break;
        }
        if (rotate != 0) {
            Bitmap bitmap = BitmapFactory.decodeFile(getTempFile().getPath());
            Matrix matrix = new Matrix();
            matrix.setRotate(rotate);
            Bitmap bmpRotated = Bitmap.createBitmap(bitmap, 0, 0, bitmap.getWidth(), bitmap.getHeight(), matrix, false);
            recycle(bitmap);
            return bmpRotated;
        }
    }
    catch (Exception e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
    }
    return null;
}

Answer 3

解决了的！我使用BitmapFactory inSampleSize选项调整图像的大小，并且图像根本不会丢失质量。代码：

BitmapFactory.Options bmpFactoryOptions = new BitmapFactory.Options();
bmpFactoryOptions.inJustDecodeBounds = true;
Bitmap bm = BitmapFactory.decodeFile(tempDir+"/"+photo1_path , bmpFactoryOptions);


int heightRatio = (int)Math.ceil(bmpFactoryOptions.outHeight/(float)600);
int widthRatio = (int)Math.ceil(bmpFactoryOptions.outWidth/(float)800);

if (heightRatio > 1 || widthRatio > 1)
{
    if (heightRatio > widthRatio){
        bmpFactoryOptions.inSampleSize = heightRatio;
    } else {
        bmpFactoryOptions.inSampleSize = widthRatio; 
    } 
}

bmpFactoryOptions.inJustDecodeBounds = false;
bm = BitmapFactory.decodeFile(tempDir+"/"+photo1_path, bmpFactoryOptions);
//bm.compress(Bitmap.CompressFormat.PNG, 100, out);
/*Bitmap new_bit = Bitmap.createScaledBitmap(src , newWidth, newHeight, true);
            new_bit.compress(Bitmap.CompressFormat.PNG, 100, out);*/


// recreate the new Bitmap
src = Bitmap.createBitmap(bm, 0, 0,bm.getWidth(), bm.getHeight(), matrix, true);


//Bitmap dest = Bitmap.createScaledBitmap(new_bit , newWidth, newHeight, true);
src.compress(Bitmap.CompressFormat.PNG, 100, out);