update library/src/main/ets/downsampling/DownsampleUtils.ets.

Signed-off-by: 田双明 <tianshuangming@h-partners.com>

library/src/main/ets/downsampling/DownsampleUtils.ets

@@ -12,6 +12,8 @@
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */
+import { DownsampleStrategy } from './DownsampleStartegy';
+
 export enum SampleSizeRounding {
   /**
    * Prefer to round the sample size up so that the image is downsampled to smaller than the
@@ -26,6 +28,7 @@ export enum SampleSizeRounding {
   //（质量优先）
   QUALITY
 }
+
 export function highestOneBit(i: number): number {
   i |= (i >> 1);
   i |= (i >> 2);
@@ -33,4 +36,22 @@ export function highestOneBit(i: number): number {
   i |= (i >> 8);
   i |= (i >> 16);
   return i - (i >>> 1);
+}
+
+
+export function getScale(sourceWidth: number, sourceHeight: number, requestedWidth: number, requestedHeight: number,
+  downsampType: DownsampleStrategy
+): number {
+  if (downsampType === DownsampleStrategy.FIT_CENTER_MEMORY) {
+    const widthPercentage = requestedWidth / sourceWidth
+    const heightPercentage = requestedHeight / sourceHeight
+    return Math.min(widthPercentage, heightPercentage)
+  } else {
+    const maxIntegerFactor = Math.max(sourceHeight / requestedHeight, sourceWidth / requestedWidth);
+    return maxIntegerFactor === 0 ? 1 : 1 / highestOneBit(maxIntegerFactor);
+
+  }
+}
+export function  round(value: number): number {
+  return Math.floor(value + 0.5);
 }