Android Training精要（五）讀取Bitmap對象實際的尺寸和類型

讀取Bitmap對象實際的尺寸和類型

BitmapFactory.Options options = new BitmapFactory.Options();

options.inJustDecodeBounds = true;

BitmapFactory.decodeResource(getResources(), R.id.myimage, options);

int imageHeight = options.outHeight;

int imageWidth = options.outWidth;

String imageType = options.outMimeType;

計算inSampleSize來控制縮放比例,值最好設為2的指數.例如inSampleSize為2,則長和寬縮短為原來的1/2,這樣整個圖片縮小為原來的1/4.

完整的從資源加載Bitmap的代碼

public static Bitmap decodeSampledBitmapFromResource(Resources res, int resId,

        int reqWidth, int reqHeight) {

    // First decode with inJustDecodeBounds=true to check dimensions

    final BitmapFactory.Options options = new BitmapFactory.Options();

    options.inJustDecodeBounds = true;

    BitmapFactory.decodeResource(res, resId, options);

    // Calculate inSampleSize

    options.inSampleSize = calculateInSampleSize(options, reqWidth, reqHeight);

    // Decode bitmap with inSampleSize set

    options.inJustDecodeBounds = false;

    return BitmapFactory.decodeResource(res, resId, options);

}

public static int calculateInSampleSize(BitmapFactory.Options options, int reqWidth, int reqHeight) {

    	// Raw height and width of image

    	final int height = options.outHeight;

    	final int width = options.outWidth;

    	int inSampleSize = 1;    

    	if (height > reqHeight || width > reqWidth) {

    		final int halfHeight = height / 2;

    		final int halfWidth = width / 2;

    		// Calculate the largest inSampleSize value that is a power of 2 and keeps both

    		// height and width larger than the requested height and width.

    		while ((halfHeight / inSampleSize) > reqHeight

    				&& (halfWidth / inSampleSize) > reqWidth) {

    			inSampleSize *= 2;

    			}

    		}

    	return inSampleSize;

    }

巴特西

Android Training精要（五）讀取Bitmap對象實際的尺寸和類型

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