问安卓:使用比双线性(如Lanczos3)更好的重采样算法调整位图大小

EN

public static void scaleImageToResolution(Context context, File image, int dstWidth, int dstHeight) {
    if (dstHeight > 0 && dstWidth > 0 && image != null) {

        Bitmap result = null;
        try {
            //Get Image Properties
            BitmapFactory.Options bmOptions = new BitmapFactory.Options();
            bmOptions.inJustDecodeBounds = true;
            BitmapFactory.decodeFile(image.getAbsolutePath(), bmOptions);
            int photoH = bmOptions.outHeight;
            int photoW = bmOptions.outWidth;

            bmOptions.inJustDecodeBounds = false;
            bmOptions.inPurgeable = true;
            //Smaller Image Size in Memory with Config
            bmOptions.inPreferredConfig = Bitmap.Config.RGB_565;

            //Is resolution not the same like 16:9 == 4:3 then crop otherwise fit
            ScalingLogic scalingLogic = getScalingLogic(photoW, photoH,dstWidth, dstHeight);
            //Get Maximum automatic downscaling that it's still bigger then this requested resolution
            bmOptions.inSampleSize = calculateScalingSampleSize(photoW, photoH, dstWidth, dstHeight, scalingLogic);

            //Get unscaled Bitmap
            result = BitmapFactory.decodeFile(image.getAbsolutePath(), bmOptions);

            //Scale Bitmap to requested Resolution
            result = scaleImageToResolution(context, result, scalingLogic);

            if (result != null) {
                //Save Bitmap with quality
                saveImageWithQuality(context, result, image);
            }
        } finally {
            //Clear Memory
            if (result != null)
                result.recycle();
        }
    }
}


public static void saveImageWithQuality(Bitmap bitmap, String path, int compressQuality) {
    try {
        FileOutputStream fOut;
        fOut = new FileOutputStream(path);
        bitmap.compress(Bitmap.CompressFormat.JPEG, compressQuality, fOut);
        fOut.flush();
        fOut.close();
    } catch (IOException ex) {
        if (Logger.getRootLogger() != null)
            Logger.getRootLogger().error(ex);
        else
            Log.e("saveImageWithQuality", "Error while saving compressed Picture: " + ex.getMessage() + StringUtils.newLine() + ex.getStackTrace().toString());
    }
}

public static void saveImageWithQuality(Context context, Bitmap bitmap, File file) {
    saveImageWithQuality(bitmap, file.getAbsolutePath(), getCompressQuality());
}

public static void saveImageWithQuality(Context context, Bitmap bitmap, String path) {
    saveImageWithQuality(bitmap, path, getCompressQuality());
}

private static int calculateScalingSampleSize(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;
        }
    }
}

private static Bitmap scaleImageToResolution(Context context, Bitmap unscaledBitmap, ScalingLogic scalingLogic, int dstWidth, int dstHeight) {
    //Do Rectangle of original picture when crop
    Rect srcRect = calculateSrcRect(unscaledBitmap.getWidth(), unscaledBitmap.getHeight(), dstWidth, dstHeight, scalingLogic);
    //Do Rectangle to fit in the source rectangle
    Rect dstRect = calculateDstRect(unscaledBitmap.getWidth(), unscaledBitmap.getHeight(), dstWidth, dstHeight, scalingLogic);
    //insert source rectangle into new one
    Bitmap scaledBitmap = Bitmap.createBitmap(dstRect.width(), dstRect.height(), Bitmap.Config.ARGB_8888);
    Canvas canvas = new Canvas(scaledBitmap);
    canvas.drawBitmap(unscaledBitmap, srcRect, dstRect, new Paint(Paint.FILTER_BITMAP_FLAG));
    //Recycle the unscaled Bitmap afterwards
    unscaledBitmap.recycle();

    return scaledBitmap;
}

private static Rect calculateSrcRect(int srcWidth, int srcHeight, int dstWidth, int dstHeight, ScalingLogic scalingLogic) {
    if (scalingLogic == ScalingLogic.CROP) {
        if (srcWidth >= srcHeight) {
            //Horizontal
            final float srcAspect = (float) srcWidth / (float) srcHeight;
            final float dstAspect = (float) dstWidth / (float) dstHeight;

            if (srcAspect < dstAspect || isResolutionEqual(srcAspect, dstAspect)) {
                final int srcRectHeight = (int) (srcWidth / dstAspect);
                final int scrRectTop = (srcHeight - srcRectHeight) / 2;
                return new Rect(0, scrRectTop, srcWidth, scrRectTop + srcRectHeight);
            } else {
                final int srcRectWidth = (int) (srcHeight * dstAspect);
                final int srcRectLeft = (srcWidth - srcRectWidth) / 2;
                return new Rect(srcRectLeft, 0, srcRectLeft + srcRectWidth, srcHeight);
            }
        } else {
            //Vertikal
            final float srcAspect = (float) srcHeight / (float) srcWidth;
            final float dstAspect = (float) dstWidth / (float) dstHeight;

            if (srcAspect < dstAspect || isResolutionEqual(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 = (srcHeight - srcRectHeight) / 2;
                return new Rect(0, scrRectTop, srcWidth, scrRectTop + srcRectHeight);
            }
        }
    } else {
        return new Rect(0, 0, srcWidth, srcHeight);
    }
}

private static Rect calculateDstRect(int srcWidth, int srcHeight, int dstWidth, int dstHeight, ScalingLogic scalingLogic) {
    if (scalingLogic == ScalingLogic.FIT) {
        if (srcWidth > srcHeight) {
            //Vertikal
            final float srcAspect = (float) srcWidth / (float) srcHeight;
            final float dstAspect = (float) dstWidth / (float) dstHeight;

            if (srcAspect < dstAspect || isResolutionEqual(srcAspect, dstAspect)) {
                return new Rect(0, 0, (int) (dstHeight * srcAspect), dstHeight);
            } else {
                return new Rect(0, 0, dstWidth, (int) (dstWidth / srcAspect));
            }
        } else {
            //Horizontal
            final float srcAspect = (float) srcHeight / (float) srcWidth;
            final float dstAspect = (float) dstWidth / (float) dstHeight;

            if (srcAspect < dstAspect || isResolutionEqual(srcAspect, dstAspect)) {
                return new Rect(0, 0, (int) (dstHeight / srcAspect), dstHeight);
            } else {
                return new Rect(0, 0, dstWidth, (int) (dstWidth * srcAspect));
            }
        }
    } else {
        if (srcWidth >= srcHeight)
            return new Rect(0, 0, dstWidth, dstHeight);
        else
            return new Rect(0, 0, dstHeight, dstWidth);
    }
}

private static ScalingLogic getScalingLogic(int imageWidth, int imageHeight, int dstResolutionWidth, int dstResolutionHeight) {
    if (imageWidth >= imageHeight) {
        //Bild horizontal
        final float srcAspect = (float) imageWidth / (float) imageHeight;
        final float dstAspect = (float) dstResolutionWidth / (float) dstResolutionHeight;
        if (!isResolutionEqual(srcAspect, dstAspect)) {
            return ScalingLogic.CROP;
        } else {
            return ScalingLogic.FIT;
        }
    } else {
        //Bild vertikal
        final float srcAspect = (float) imageHeight / (float) imageWidth;
        final float dstAspect = (float) dstResolutionWidth / (float) dstResolutionHeight;
        if (!isResolutionEqual(srcAspect, dstAspect)) {
            return ScalingLogic.CROP;
        } else {
            return ScalingLogic.FIT;
        }
    }
}

public enum PictureQuality {
    High,
    Medium,
    Low
}

public enum ScalingLogic {
    CROP,
    FIT
}

//Does resolution match
private static boolean isResolutionEqual(float v1, float v2) {
    // Falls a 1.999999999999 and b = 2.000000000000
    return v1 == v2 || Math.abs(v1 - v2) / Math.max(Math.abs(v1), Math.abs(v2)) < 0.01;
}

public int getCompressQuality() {
    if (Quality == PictureQuality.High)
        return 100;
    else if (Quality == PictureQuality.Medium)
        return 50;
    else if (Quality == PictureQuality.Low)
        return 25;
    else return 0;
}