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November 11, 2015 15:39
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import android.content.res.Resources; | |
import android.graphics.Bitmap; | |
import android.graphics.Bitmap.Config; | |
import android.graphics.BitmapFactory; | |
import android.graphics.BitmapFactory.Options; | |
import android.graphics.Canvas; | |
import android.graphics.Paint; | |
import android.graphics.Rect; | |
/** | |
* Class containing static utility methods for bitmap decoding and scaling | |
* | |
* @author | |
*/ | |
public class ScalingUtilities { | |
/** | |
* Utility function for decoding an image resource. The decoded bitmap will | |
* be optimized for further scaling to the requested destination dimensions | |
* and scaling logic. | |
* | |
* @param res The resources object containing the image data | |
* @param resId The resource id of the image data | |
* @param dstWidth Width of destination area | |
* @param dstHeight Height of destination area | |
* @param scalingLogic Logic to use to avoid image stretching | |
* @return Decoded bitmap | |
*/ | |
public static Bitmap decodeResource(Resources res, int resId, int dstWidth, int dstHeight, | |
ScalingLogic scalingLogic) { | |
Options options = new Options(); | |
options.inJustDecodeBounds = true; | |
BitmapFactory.decodeResource(res, resId, options); | |
options.inJustDecodeBounds = false; | |
options.inSampleSize = calculateSampleSize(options.outWidth, options.outHeight, dstWidth, | |
dstHeight, scalingLogic); | |
Bitmap unscaledBitmap = BitmapFactory.decodeResource(res, resId, options); | |
return unscaledBitmap; | |
} | |
public static Bitmap decodeFile(String path, int dstWidth, int dstHeight, | |
ScalingLogic scalingLogic) { | |
Options options = new Options(); | |
options.inJustDecodeBounds = true; | |
BitmapFactory.decodeFile(path, options); | |
options.inJustDecodeBounds = false; | |
options.inSampleSize = calculateSampleSize(options.outWidth, options.outHeight, dstWidth, | |
dstHeight, scalingLogic); | |
Bitmap unscaledBitmap = BitmapFactory.decodeFile(path, options); | |
return unscaledBitmap; | |
} | |
/** | |
* Utility function for creating a scaled version of an existing bitmap | |
* | |
* @param unscaledBitmap Bitmap to scale | |
* @param dstWidth Wanted width of destination bitmap | |
* @param dstHeight Wanted height of destination bitmap | |
* @param scalingLogic Logic to use to avoid image stretching | |
* @return New scaled bitmap object | |
*/ | |
public static Bitmap createScaledBitmap(Bitmap unscaledBitmap, int dstWidth, int dstHeight, | |
ScalingLogic scalingLogic) { | |
Rect srcRect = calculateSrcRect(unscaledBitmap.getWidth(), unscaledBitmap.getHeight(), | |
dstWidth, dstHeight, scalingLogic); | |
Rect dstRect = calculateDstRect(unscaledBitmap.getWidth(), unscaledBitmap.getHeight(), | |
dstWidth, dstHeight, scalingLogic); | |
Bitmap scaledBitmap = Bitmap.createBitmap(dstRect.width(), dstRect.height(), | |
Config.ARGB_8888); | |
Canvas canvas = new Canvas(scaledBitmap); | |
canvas.drawBitmap(unscaledBitmap, srcRect, dstRect, new Paint(Paint.FILTER_BITMAP_FLAG)); | |
return scaledBitmap; | |
} | |
/** | |
* ScalingLogic defines how scaling should be carried out if source and | |
* destination image has different aspect ratio. | |
* | |
* CROP: Scales the image the minimum amount while making sure that at least | |
* one of the two dimensions fit inside the requested destination area. | |
* Parts of the source image will be cropped to realize this. | |
* | |
* FIT: Scales the image the minimum amount while making sure both | |
* dimensions fit inside the requested destination area. The resulting | |
* destination dimensions might be adjusted to a smaller size than | |
* requested. | |
*/ | |
public static enum ScalingLogic { | |
CROP, FIT | |
} | |
/** | |
* Calculate optimal down-sampling factor given the dimensions of a source | |
* image, the dimensions of a destination area and a scaling logic. | |
* | |
* @param srcWidth Width of source image | |
* @param srcHeight Height of source image | |
* @param dstWidth Width of destination area | |
* @param dstHeight Height of destination area | |
* @param scalingLogic Logic to use to avoid image stretching | |
* @return Optimal down scaling sample size for decoding | |
*/ | |
public static int calculateSampleSize(int srcWidth, int srcHeight, int dstWidth, int dstHeight, | |
ScalingLogic scalingLogic) { | |
if (scalingLogic == ScalingLogic.FIT) { | |
final float srcAspect = (float)srcWidth / (float)srcHeight; | |
final float dstAspect = (float)dstWidth / (float)dstHeight; | |
if (srcAspect > dstAspect) { | |
return srcWidth / dstWidth; | |
} else { | |
return srcHeight / dstHeight; | |
} | |
} else { | |
final float srcAspect = (float)srcWidth / (float)srcHeight; | |
final float dstAspect = (float)dstWidth / (float)dstHeight; | |
if (srcAspect > dstAspect) { | |
return srcHeight / dstHeight; | |
} else { | |
return srcWidth / dstWidth; | |
} | |
} | |
} | |
/** | |
* Calculates source rectangle for scaling bitmap | |
* | |
* @param srcWidth Width of source image | |
* @param srcHeight Height of source image | |
* @param dstWidth Width of destination area | |
* @param dstHeight Height of destination area | |
* @param scalingLogic Logic to use to avoid image stretching | |
* @return Optimal source rectangle | |
*/ | |
public static Rect calculateSrcRect(int srcWidth, int srcHeight, int dstWidth, int dstHeight, | |
ScalingLogic scalingLogic) { | |
if (scalingLogic == ScalingLogic.CROP) { | |
final float srcAspect = (float)srcWidth / (float)srcHeight; | |
final float dstAspect = (float)dstWidth / (float)dstHeight; | |
if (srcAspect > dstAspect) { | |
final int srcRectWidth = (int)(srcHeight * dstAspect); | |
final int srcRectLeft = (srcWidth - srcRectWidth) / 2; | |
return new Rect(srcRectLeft, 0, srcRectLeft + srcRectWidth, srcHeight); | |
} else { | |
final int srcRectHeight = (int)(srcWidth / dstAspect); | |
final int scrRectTop = (int)(srcHeight - srcRectHeight) / 2; | |
return new Rect(0, scrRectTop, srcWidth, scrRectTop + srcRectHeight); | |
} | |
} else { | |
return new Rect(0, 0, srcWidth, srcHeight); | |
} | |
} | |
/** | |
* Calculates destination rectangle for scaling bitmap | |
* | |
* @param srcWidth Width of source image | |
* @param srcHeight Height of source image | |
* @param dstWidth Width of destination area | |
* @param dstHeight Height of destination area | |
* @param scalingLogic Logic to use to avoid image stretching | |
* @return Optimal destination rectangle | |
*/ | |
public static Rect calculateDstRect(int srcWidth, int srcHeight, int dstWidth, int dstHeight, | |
ScalingLogic scalingLogic) { | |
if (scalingLogic == ScalingLogic.FIT) { | |
final float srcAspect = (float)srcWidth / (float)srcHeight; | |
final float dstAspect = (float)dstWidth / (float)dstHeight; | |
if (srcAspect > dstAspect) { | |
return new Rect(0, 0, dstWidth, (int)(dstWidth / srcAspect)); | |
} else { | |
return new Rect(0, 0, (int)(dstHeight * srcAspect), dstHeight); | |
} | |
} else { | |
return new Rect(0, 0, dstWidth, dstHeight); | |
} | |
} | |
} |
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