ios和android中的whatsapp和instagram等图像优化

Question

任务：- 像 Facebook 和 WhatApp 一样优化图像？ 在android和ios中上传图片到服务器，优化尺寸，不损失图片质量和尺寸。

我见过很多代码，例如原生图像压缩 (UIImageJPEGRepresentation(viewImage, 0.8))，但我无法得到正确的结果。

谁能给我推荐 iOS 和 android 中的任何算法或库，通过它们我们可以优化图像而不会损失质量。

我已经访问过的链接：

iOS

1. What's the easiest way to resize/optimize an image size with the iPhone SDK?

安卓

1. https://abdelhady.net/2015/03/28/android-loading-images-super-fast-like-whatsapp-part-2/
2. https://gist.github.com/vipulasri/0cd97d012934531f1266
3. http://voidcanvas.com/whatsapp-like-image-compression-in-android/

Answer 1

试试这个代码：

+(UIImage *)scaleAndRotateImage:(UIImage *)image {
int kMaxResolution = 640; // Or whatever

CGImageRef imgRef = image.CGImage;

CGFloat width = CGImageGetWidth(imgRef);
CGFloat height = CGImageGetHeight(imgRef);


CGAffineTransform transform = CGAffineTransformIdentity;
CGRect bounds = CGRectMake(0, 0, width, height);
if (width > kMaxResolution || height > kMaxResolution) {
    CGFloat ratio = width/height;
    if (ratio > 1) {
        bounds.size.width = kMaxResolution;
        bounds.size.height = roundf(bounds.size.width / ratio);
    }
    else {
        bounds.size.height = kMaxResolution;
        bounds.size.width = roundf(bounds.size.height * ratio);
    }
}

CGFloat scaleRatio = bounds.size.width / width;
CGSize imageSize = CGSizeMake(CGImageGetWidth(imgRef), CGImageGetHeight(imgRef));
CGFloat boundHeight;
UIImageOrientation orient = image.imageOrientation;
switch(orient) {

    case UIImageOrientationUp: //EXIF = 1
        transform = CGAffineTransformIdentity;
        break;

    case UIImageOrientationUpMirrored: //EXIF = 2
        transform = CGAffineTransformMakeTranslation(imageSize.width, 0.0);
        transform = CGAffineTransformScale(transform, -1.0, 1.0);
        break;

    case UIImageOrientationDown: //EXIF = 3
        transform = CGAffineTransformMakeTranslation(imageSize.width, imageSize.height);
        transform = CGAffineTransformRotate(transform, M_PI);
        break;

    case UIImageOrientationDownMirrored: //EXIF = 4
        transform = CGAffineTransformMakeTranslation(0.0, imageSize.height);
        transform = CGAffineTransformScale(transform, 1.0, -1.0);
        break;

    case UIImageOrientationLeftMirrored: //EXIF = 5
        boundHeight = bounds.size.height;
        bounds.size.height = bounds.size.width;
        bounds.size.width = boundHeight;
        transform = CGAffineTransformMakeTranslation(imageSize.height, imageSize.width);
        transform = CGAffineTransformScale(transform, -1.0, 1.0);
        transform = CGAffineTransformRotate(transform, 3.0 * M_PI / 2.0);
        break;

    case UIImageOrientationLeft: //EXIF = 6
        boundHeight = bounds.size.height;
        bounds.size.height = bounds.size.width;
        bounds.size.width = boundHeight;
        transform = CGAffineTransformMakeTranslation(0.0, imageSize.width);
        transform = CGAffineTransformRotate(transform, 3.0 * M_PI / 2.0);
        break;

    case UIImageOrientationRightMirrored: //EXIF = 7
        boundHeight = bounds.size.height;
        bounds.size.height = bounds.size.width;
        bounds.size.width = boundHeight;
        transform = CGAffineTransformMakeScale(-1.0, 1.0);
        transform = CGAffineTransformRotate(transform, M_PI / 2.0);
        break;

    case UIImageOrientationRight: //EXIF = 8
        boundHeight = bounds.size.height;
        bounds.size.height = bounds.size.width;
        bounds.size.width = boundHeight;
        transform = CGAffineTransformMakeTranslation(imageSize.height, 0.0);
        transform = CGAffineTransformRotate(transform, M_PI / 2.0);
        break;

    default:
        [NSException raise:NSInternalInconsistencyException format:@"Invalid image orientation"];

}

UIGraphicsBeginImageContext(bounds.size);
CGContextRef context = UIGraphicsGetCurrentContext();

if (orient == UIImageOrientationRight || orient == UIImageOrientationLeft) {
    CGContextScaleCTM(context, -scaleRatio, scaleRatio);
    CGContextTranslateCTM(context, -height, 0);
}
else {
    CGContextScaleCTM(context, scaleRatio, -scaleRatio);
    CGContextTranslateCTM(context, 0, -height);
}

CGContextConcatCTM(context, transform);

CGContextDrawImage(UIGraphicsGetCurrentContext(), CGRectMake(0, 0, width, height), imgRef);
UIImage *imageCopy = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();

CGFloat scaleSize = 0.2f;
UIImage *smallImage = [UIImage imageWithCGImage:imageCopy.CGImage
                                          scale:scaleSize
                                    orientation:imageCopy.imageOrientation];

return smallImage;
}

Answer 2

这是我在 Android 中使用的：

public class ImageCompresser {

    public static void compressImage(String inputFilePath, String outputFilePath) {
        try {

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

            BitmapFactory.decodeFile(inputFilePath, options);

            //options.inSampleSize = calculateInSampleSize(options,400,300);
            options.inSampleSize = calculateInSampleSize(options,800,1000);//Specify Minimum Height, Width of the resulting bitmap maintaining the aspect ratio

            options.inJustDecodeBounds = false;

            Bitmap bm = BitmapFactory.decodeFile(inputFilePath, options);

            FileOutputStream fileOutputStream;

            fileOutputStream = new FileOutputStream(outputFilePath);

            ExifInterface exif;
            try {
                exif = new ExifInterface(inputFilePath);

                Log.d("EXIF", "Make : " + exif.getAttribute(ExifInterface.TAG_MAKE));

                int orientation = exif.getAttributeInt(
                        ExifInterface.TAG_ORIENTATION, 0);
                Log.d("EXIF", "Exif Orientation : " + orientation);
                Matrix matrix = new Matrix();
                if (orientation == 6) {
                    matrix.postRotate(90);
                    Log.d("EXIF", "Exif: " + orientation);
                } else if (orientation == 3) {
                    matrix.postRotate(180);
                    Log.d("EXIF", "Exif: " + orientation);
                } else if (orientation == 8) {
                    matrix.postRotate(270);
                    Log.d("EXIF", "Exif: " + orientation);
                }
                Bitmap scaledBitmap = Bitmap.createBitmap(bm, 0, 0,
                        bm.getWidth(), bm.getHeight(), matrix,
                        true);

                scaledBitmap.compress(Bitmap.CompressFormat.JPEG, 100, fileOutputStream);//Instead of 100, you can provide any value. But it will reduce the image quality 
                scaledBitmap.recycle();
            } catch (IOException e) {
                e.printStackTrace();
            }

            fileOutputStream.flush();
            fileOutputStream.close();
            bm.recycle();
        } catch (FileNotFoundException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        } 
    }

    private static int calculateInSampleSize(BitmapFactory.Options options, int reqWidth, int reqHeight) {
        final int imageWidth = options.outWidth;
        final int imageHeight = options.outHeight;
        Log.d("Test", "imageWidth : " + imageWidth);
        Log.d("Test", "imageHeight : " + imageHeight);

        int inSampleSize = 1;

        if(imageWidth > reqWidth || imageHeight > reqHeight) {
            final int halfWidth = imageWidth / 2;
            final int halfHeight = imageHeight / 2;

            while((halfWidth / inSampleSize) > reqWidth
                    && (halfHeight / inSampleSize) > reqHeight) {
                inSampleSize *= 2;
            }
        }

        return inSampleSize;
    }
}

参考文献：

1. http://voidcanvas.com/whatsapp-like-image-compression-in-android/
2. https://developer.android.com/training/displaying-bitmaps/load-bitmap.html