我有一个位图采取的Base64字符串从我的远程数据库,(encodedImage是字符串表示图像与Base64):

profileImage = (ImageView)findViewById(R.id.profileImage);

byte[] imageAsBytes=null;
try {
    imageAsBytes = Base64.decode(encodedImage.getBytes());
} catch (IOException e) {e.printStackTrace();}

profileImage.setImageBitmap(
    BitmapFactory.decodeByteArray(imageAsBytes, 0, imageAsBytes.length)
);

profileImage是我的ImageView

但在显示在布局的ImageView中之前,我需要调整图像的大小。我得把它调整到120x120。

有人能告诉我调整大小的代码吗?

我发现的例子不能应用于base64字符串获得位图。


当前回答

缩放位图的目标最大大小和宽度,同时保持纵横比:

int maxHeight = 2000;
int maxWidth = 2000;    
float scale = Math.min(((float)maxHeight / bitmap.getWidth()), ((float)maxWidth / bitmap.getHeight()));

Matrix matrix = new Matrix();
matrix.postScale(scale, scale);

bitmap = Bitmap.createBitmap(bitmap, 0, 0, bitmap.getWidth(), bitmap.getHeight(), matrix, true);

其他回答

基于纵横比的规模:

float aspectRatio = yourSelectedImage.getWidth() / 
    (float) yourSelectedImage.getHeight();
int width = 480;
int height = Math.round(width / aspectRatio);

yourSelectedImage = Bitmap.createScaledBitmap(
    yourSelectedImage, width, height, false);

使用高度作为基础而不是宽度更改为:

int height = 480;
int width = Math.round(height * aspectRatio);

虽然前面的答案确实缩放了图像并考虑了纵横比,但重新采样本身应该这样做,这样就不会出现混叠。注意尺度是一个正确修正参数的问题。有许多关于标准缩放调用输出图像质量的评论。为了保持图像的质量,应该使用标准调用:

位图resizedBitmap =位图。createScaledBitmap(originalBitmap, newWidth, newHeight, true);

最后一个参数设置为true,因为它将对重采样进行双线性过滤,以防止混叠。在这里阅读更多关于别名的信息:https://en.wikipedia.org/wiki/Aliasing

来自android文档:

https://developer.android.com/reference/android/graphics/Bitmap createScaledBitmap (android.graphics.Bitmap % 20 int, int % 20, % 20布尔)


public static Bitmap createScaledBitmap (Bitmap src, 
                int dstWidth, 
                int dstHeight, 
                boolean filter)

filter: boolean,当缩放位图时是否应该使用双线性过滤。如果这是真的,那么在缩放时将使用双线性滤波,它以更差的性能为代价,具有更好的图像质量。如果这是假的,那么使用最近邻缩放,这将有较差的图像质量,但更快。推荐的默认值是将filter设置为'true',因为双线性过滤的成本通常是最小的,并且图像质量的改善是显著的。

* For resize bitmap with width and height ratio.    

public static Bitmap getResizedBitmap(Bitmap image, int maxSize) {
            int width = image.getWidth();
            int height = image.getHeight();
    
            float bitmapRatio = (float) width / (float) height;
            if (bitmapRatio > 1) {
                width = maxSize;
                height = (int) (width / bitmapRatio);
            } else {
                height = maxSize;
                width = (int) (height * bitmapRatio);
            }
            return Bitmap.createScaledBitmap(image, width, height, true);
        }

保持纵横比,

  public Bitmap resizeBitmap(Bitmap source, int width,int height) {
    if(source.getHeight() == height && source.getWidth() == width) return source;
    int maxLength=Math.min(width,height);
    try {
        source=source.copy(source.getConfig(),true);
        if (source.getHeight() <= source.getWidth()) {
            if (source.getHeight() <= maxLength) { // if image already smaller than the required height
                return source;
            }

            double aspectRatio = (double) source.getWidth() / (double) source.getHeight();
            int targetWidth = (int) (maxLength * aspectRatio);

            return Bitmap.createScaledBitmap(source, targetWidth, maxLength, false);
        } else {

            if (source.getWidth() <= maxLength) { // if image already smaller than the required height
                return source;
            }

            double aspectRatio = ((double) source.getHeight()) / ((double) source.getWidth());
            int targetHeight = (int) (maxLength * aspectRatio);

            return Bitmap.createScaledBitmap(source, maxLength, targetHeight, false);

        }
    }
    catch (Exception e)
    {
        return source;
    }
}
profileImage.setImageBitmap(
    Bitmap.createScaledBitmap(
        BitmapFactory.decodeByteArray(imageAsBytes, 0, imageAsBytes.length), 
        80, 80, false
    )
);