diff options
Diffstat (limited to 'docs/html/training/displaying-bitmaps/load-bitmap.jd')
| -rw-r--r-- | docs/html/training/displaying-bitmaps/load-bitmap.jd | 27 |
1 files changed, 14 insertions, 13 deletions
diff --git a/docs/html/training/displaying-bitmaps/load-bitmap.jd b/docs/html/training/displaying-bitmaps/load-bitmap.jd index 633ffd2..938901f 100644 --- a/docs/html/training/displaying-bitmaps/load-bitmap.jd +++ b/docs/html/training/displaying-bitmaps/load-bitmap.jd @@ -97,7 +97,8 @@ android.graphics.BitmapFactory.Options} object. For example, an image with resol is decoded with an {@link android.graphics.BitmapFactory.Options#inSampleSize} of 4 produces a bitmap of approximately 512x384. Loading this into memory uses 0.75MB rather than 12MB for the full image (assuming a bitmap configuration of {@link android.graphics.Bitmap.Config ARGB_8888}). Here’s -a method to calculate a the sample size value based on a target width and height:</p> +a method to calculate a sample size value that is a power of two based on a target width and +height:</p> <pre> public static int calculateInSampleSize( @@ -107,26 +108,26 @@ public static int calculateInSampleSize( final int width = options.outWidth; int inSampleSize = 1; - if (height > reqHeight || width > reqWidth) { + if (height > reqHeight || width > reqWidth) { - // Calculate ratios of height and width to requested height and width - final int heightRatio = Math.round((float) height / (float) reqHeight); - final int widthRatio = Math.round((float) width / (float) reqWidth); + final int halfHeight = height / 2; + final int halfWidth = width / 2; - // Choose the smallest ratio as inSampleSize value, this will guarantee - // a final image with both dimensions larger than or equal to the - // requested height and width. - inSampleSize = heightRatio < widthRatio ? heightRatio : widthRatio; + // 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; } </pre> -<p class="note"><strong>Note:</strong> Using powers of 2 for {@link -android.graphics.BitmapFactory.Options#inSampleSize} values is faster and more efficient for the -decoder. However, if you plan to cache the resized versions in memory or on disk, it’s usually still -worth decoding to the most appropriate image dimensions to save space.</p> +<p class="note"><strong>Note:</strong> A power of two value is calculated because the decoder uses +a final value by rounding down to the nearest power of two, as per the {@link +android.graphics.BitmapFactory.Options#inSampleSize} documentation.</p> <p>To use this method, first decode with {@link android.graphics.BitmapFactory.Options#inJustDecodeBounds} set to {@code true}, pass the options |