Android - 减小图像文件大小 [英] Android - Reduce image file size

问题描述

我有一个 URI 图像文件，我想减小它的大小以上传它.初始图像文件大小取决于移动设备(可以是 2MB，也可以是 500KB)，但我希望最终大小约为 200KB，以便我可以上传.
从我读到的内容来看，我(至少)有 2 个选择:

I have an URI image file, and I want to reduce its size to upload it. Initial image file size depends from mobile to mobile (can be 2MB as can be 500KB), but I want final size to be about 200KB, so that I can upload it.
From what I read, I have (at least) 2 choices:

• 使用BitmapFactory.Options.inSampleSize，对原始图像进行二次采样并获得较小的图像；
  
• 使用 Bitmap.compress 来压缩指定压缩质量的图像.
  

• Using BitmapFactory.Options.inSampleSize, to subsample original image and get a smaller image;
  
• Using Bitmap.compress to compress the image specifying compression quality.
  

最好的选择是什么?

我想最初调整图像的宽度/高度，直到宽度或高度超过 1000 像素(例如 1024x768 或其他)，然后以降低的质量压缩图像，直到文件大小超过 200KB.下面是一个例子:

I was thinking to initially resize image width/height until width or height is above 1000px (something like 1024x768 or others), then compress image with decreasing quality until file size is above 200KB. Here's an example:

int MAX_IMAGE_SIZE = 200 * 1024; // max final file size
Bitmap bmpPic = BitmapFactory.decodeFile(fileUri.getPath());
if ((bmpPic.getWidth() >= 1024) && (bmpPic.getHeight() >= 1024)) {
    BitmapFactory.Options bmpOptions = new BitmapFactory.Options();
    bmpOptions.inSampleSize = 1;
    while ((bmpPic.getWidth() >= 1024) && (bmpPic.getHeight() >= 1024)) {
        bmpOptions.inSampleSize++;
        bmpPic = BitmapFactory.decodeFile(fileUri.getPath(), bmpOptions);
    }
    Log.d(TAG, "Resize: " + bmpOptions.inSampleSize);
}
int compressQuality = 104; // quality decreasing by 5 every loop. (start from 99)
int streamLength = MAX_IMAGE_SIZE;
while (streamLength >= MAX_IMAGE_SIZE) {
    ByteArrayOutputStream bmpStream = new ByteArrayOutputStream();
    compressQuality -= 5;
    Log.d(TAG, "Quality: " + compressQuality);
    bmpPic.compress(Bitmap.CompressFormat.JPEG, compressQuality, bmpStream);
    byte[] bmpPicByteArray = bmpStream.toByteArray();
    streamLength = bmpPicByteArray.length;
    Log.d(TAG, "Size: " + streamLength);
}
try {
    FileOutputStream bmpFile = new FileOutputStream(finalPath);
    bmpPic.compress(Bitmap.CompressFormat.JPEG, compressQuality, bmpFile);
    bmpFile.flush();
    bmpFile.close();
} catch (Exception e) {
    Log.e(TAG, "Error on saving file");
}

有没有更好的方法来做到这一点?我应该尝试继续使用所有 2 种方法还是仅使用一种?谢谢

Is there a better way to do it? Should I try to keep using all 2 methods or only one? Thanks

推荐答案

使用 Bitmap.compress() 您只需指定压缩算法，顺便说一下，压缩操作需要相当长的时间.如果您需要调整大小以减少图像的内存分配，您需要使用 Bitmap.Options 缩放图像，首先计算位图边界，然后将其解码为指定的大小.

Using Bitmap.compress() you just specify compression algorithm and by the way compression operation takes rather big amount of time. If you need to play with sizes for reducing memory allocation for your image, you exactly need to use scaling of your image using Bitmap.Options, computing bitmap bounds at first and then decoding it to your specified size.

我在 StackOverflow 上找到的最好的示例是这个.

The best sample that I found on StackOverflow is this one.

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