Android开发中优化图片质量与处理图片旋转的实用指南

// 示例：启动相机并保存全尺寸图片
private Uri imageUri; // 用于保存图片URI

private void dispatchTakePictureIntent() {
    Intent takePictureIntent = new Intent(MediaStore.ACTION_IMAGE_CAPTURE);
    if (takePictureIntent.resolveActivity(getPackageManager()) != null) {
        File photoFile = null;
        try {
            photoFile = createImageFile(); // 创建一个临时文件来保存图片
        } catch (IOException ex) {
            // 错误处理
        }
        if (photoFile != null) {
            imageUri = FileProvider.getUriForFile(this,
                    "com.example.android.fileprovider", // 替换为你的FileProvider authority
                    photoFile);
            takePictureIntent.putExtra(MediaStore.EXTRA_OUTPUT, imageUri);
            startActivityForResult(takePictureIntent, REQUEST_IMAGE_CAPTURE);
        }
    }
}

// 示例：创建图片文件
private File createImageFile() throws IOException {
    String timeStamp = new SimpleDateFormat("yyyyMMdd_HHmmss", Locale.getDefault()).format(new Date());
    String imageFileName = "JPEG_" + timeStamp + "_";
    File storageDir = getExternalFilesDir(Environment.DIRECTORY_PICTURES);
    File image = File.createTempFile(
            imageFileName,  /* prefix */
            ".jpg",         /* suffix */
            storageDir      /* directory */
    );
    return image;
}

// 在 onActivityResult 中获取图片
@Override
protected void onActivityResult(int requestCode, int resultCode, Intent data) {
    super.onActivityResult(requestCode, resultCode, data);
    if (requestCode == REQUEST_IMAGE_CAPTURE && resultCode == RESULT_OK) {
        try {
            Bitmap fullSizeBitmap = MediaStore.Images.Media.getBitmap(this.getContentResolver(), imageUri);
            // 现在 fullSizeBitmap 是全尺寸的，可以进行后续处理
            // ...
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}

/**
 * 等比例缩放Bitmap，使其最大边长不超过maxSize
 * @param myBitmap 原始Bitmap
 * @param maxSize 目标最大边长
 * @return 缩放后的Bitmap
 */
public Bitmap scaleBitmapAspectRatio(Bitmap myBitmap, int maxSize) {
    int inWidth = myBitmap.getWidth();
    int inHeight = myBitmap.getHeight();
    int outWidth;
    int outHeight;

    if (inWidth > inHeight) {
        outWidth = maxSize;
        outHeight = (inHeight * maxSize) / inWidth;
    } else {
        outHeight = maxSize;
        outWidth = (inWidth * maxSize) / inHeight;
    }

    // 使用createScaledBitmap进行缩放，最后一个参数为true表示使用双线性过滤，可以提高缩放质量
    return Bitmap.createScaledBitmap(myBitmap, outWidth, outHeight, true);
}

// 示例：从相册选择图片并进行缩放
else if (requestCode == REQUEST_IMAGE_PICK && resultCode == RESULT_OK) {
    Uri selectedImageUri = data.getData();
    if (selectedImageUri != null) {
        try {
            Bitmap originalBitmap = MediaStore.Images.Media.getBitmap(this.getContentResolver(), selectedImageUri);
            Bitmap scaledBitmap = scaleBitmapAspectRatio(originalBitmap, 960); // 缩放到最大边长960px
            // ... 进一步处理 scaledBitmap
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}

import android.media.ExifInterface;

/**
 * 获取图片的EXIF方向信息
 * @param imagePath 图片文件路径或Uri（需转换为文件路径）
 * @return EXIF方向值，如果无法获取则返回ExifInterface.ORIENTATION_NORMAL
 */
public int getExifOrientation(String imagePath) {
    try {
        ExifInterface exifInterface = new ExifInterface(imagePath);
        return exifInterface.getAttributeInt(ExifInterface.TAG_ORIENTATION, ExifInterface.ORIENTATION_NORMAL);
    } catch (IOException e) {
        e.printStackTrace();
        return ExifInterface.ORIENTATION_NORMAL;
    }
}

import android.graphics.Matrix;

/**
 * 根据EXIF方向旋转Bitmap
 * @param bitmap 原始Bitmap
 * @param orientation EXIF方向值 (如ExifInterface.ORIENTATION_ROTATE_90)
 * @return 旋转后的Bitmap
 */
public Bitmap rotateBitmap(Bitmap bitmap, int orientation) {
    Matrix matrix = new Matrix();
    int rotationAngle = 0;

    switch (orientation) {
        case ExifInterface.ORIENTATION_ROTATE_90:
            rotationAngle = 90;
            break;
        case ExifInterface.ORIENTATION_ROTATE_180:
            rotationAngle = 180;
            break;
        case ExifInterface.ORIENTATION_ROTATE_270:
            rotationAngle = 270;
            break;
        case ExifInterface.ORIENTATION_FLIP_HORIZONTAL: // 水平翻转
            matrix.preScale(-1, 1);
            break;
        case ExifInterface.ORIENTATION_FLIP_VERTICAL: // 垂直翻转
            matrix.preScale(1, -1);
            break;
        case ExifInterface.ORIENTATION_TRANSPOSE: // 旋转90度并水平翻转
            rotationAngle = 90;
            matrix.preScale(-1, 1);
            break;
        case ExifInterface.ORIENTATION_TRANSVERSE: // 旋转270度并水平翻转
            rotationAngle = 270;
            matrix.preScale(-1, 1);
            break;
        case ExifInterface.ORIENTATION_NORMAL:
        default:
            return bitmap; // 无需旋转
    }

    if (rotationAngle != 0) {
        matrix.postRotate(rotationAngle);
    }

    try {
        Bitmap rotatedBitmap = Bitmap.createBitmap(bitmap, 0, 0, bitmap.getWidth(), bitmap.getHeight(), matrix, true);
        if (bitmap != rotatedBitmap) {
            bitmap.recycle(); // 回收原始Bitmap以节省内存
        }
        return rotatedBitmap;
    } catch (OutOfMemoryError e) {
        e.printStackTrace();
        return bitmap; // 内存不足时返回原图
    }
}

// 假设已获取到原始Bitmap originalBitmap 和图片文件路径 imagePath
// 1. 缩放图片
Bitmap scaledBitmap = scaleBitmapAspectRatio(originalBitmap, 960);

// 2. 获取EXIF方向并旋转
// 注意：这里需要一个方法将Uri转换为文件路径，或直接使用ExifInterface(InputStream)
// 假设我们已经有了图片的文件路径 filePath
int orientation = getExifOrientation(filePath); // 或者从Uri获取InputStream并用ExifInterface(InputStream)
Bitmap finalBitmap = rotateBitmap(scaledBitmap, orientation);

// 现在 finalBitmap 是经过缩放和正确旋转的图片，可以显示或进行其他处理
imgHinh.setImageBitmap(finalBitmap);