如何在Android中调整位图大小？

时间：2011-01-29 15:38:30

标签： android bitmap base64

我的远程数据库中有一个Base64字符串的位图，（encodedImage是用Base64表示图像的字符串）：

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

好的，但是我必须在我的ImageView布局上显示之前调整此图片的大小。我必须将其调整为120x120。

有人可以告诉我调整大小的代码吗？

我找到的示例无法应用于获得位图的base64字符串。

18 个答案:

答案 0 :(得分：493)

变化：

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

要：

Bitmap b = BitmapFactory.decodeByteArray(imageAsBytes, 0, imageAsBytes.length)
profileImage.setImageBitmap(Bitmap.createScaledBitmap(b, 120, 120, false));

答案 1 :(得分：263)

public Bitmap getResizedBitmap(Bitmap bm, int newWidth, int newHeight) {
    int width = bm.getWidth();
    int height = bm.getHeight();
    float scaleWidth = ((float) newWidth) / width;
    float scaleHeight = ((float) newHeight) / height;
    // CREATE A MATRIX FOR THE MANIPULATION
    Matrix matrix = new Matrix();
    // RESIZE THE BIT MAP
    matrix.postScale(scaleWidth, scaleHeight);

    // "RECREATE" THE NEW BITMAP
    Bitmap resizedBitmap = Bitmap.createBitmap(
        bm, 0, 0, width, height, matrix, false);
    bm.recycle();
    return resizedBitmap;
}

编辑：正如@a​​veschini所建议的，我已经为内存泄漏添加了bm.recycle();。请注意，如果您将上一个对象用于其他目的，请相应处理。

答案 2 :(得分：107)

如果您已有位图，则可以使用以下代码调整大小：

Bitmap originalBitmap = <original initialization>;
Bitmap resizedBitmap = Bitmap.createScaledBitmap(
    originalBitmap, newWidth, newHeight, false);

答案 3 :(得分：35)

根据宽高比进行缩放：

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height作为宽度变化的基本intead：

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

答案 4 :(得分：22)

使用目标最大大小和宽度缩放位图，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);

答案 5 :(得分：7)

试试这段代码：

BitmapDrawable drawable = (BitmapDrawable) imgview.getDrawable();
Bitmap bmp = drawable.getBitmap();
Bitmap b = Bitmap.createScaledBitmap(bmp, 120, 120, false);

我希望它有用。

答案 6 :(得分：7)

有人问过如何在这种情况下保持纵横比：

计算用于缩放的因子，并将其用于两个维度。 假设您希望图像高度为屏幕的20％

int scaleToUse = 20; // this will be our percentage
Bitmap bmp = BitmapFactory.decodeResource(
    context.getResources(), R.drawable.mypng);
int sizeY = screenResolution.y * scaleToUse / 100;
int sizeX = bmp.getWidth() * sizeY / bmp.getHeight();
Bitmap scaled = Bitmap.createScaledBitmap(bmp, sizeX, sizeY, false);

获取屏幕分辨率，你有这个解决方案： Get screen dimensions in pixels

答案 7 :(得分：3)

profileImage.setImageBitmap(
    Bitmap.createScaledBitmap(
        BitmapFactory.decodeByteArray(imageAsBytes, 0, imageAsBytes.length), 
        80, 80, false
    )
);

答案 8 :(得分：3)

试试这个： 此函数按比例调整位图大小。当最后一个参数设置为＆＃34; X＆＃34; newDimensionXorY被视为新的宽度，当设置为＆＃34; Y＆＃34;一个新的高度。

public Bitmap getProportionalBitmap(Bitmap bitmap, 
                                    int newDimensionXorY, 
                                    String XorY) {
    if (bitmap == null) {
        return null;
    }

    float xyRatio = 0;
    int newWidth = 0;
    int newHeight = 0;

    if (XorY.toLowerCase().equals("x")) {
        xyRatio = (float) newDimensionXorY / bitmap.getWidth();
        newHeight = (int) (bitmap.getHeight() * xyRatio);
        bitmap = Bitmap.createScaledBitmap(
            bitmap, newDimensionXorY, newHeight, true);
    } else if (XorY.toLowerCase().equals("y")) {
        xyRatio = (float) newDimensionXorY / bitmap.getHeight();
        newWidth = (int) (bitmap.getWidth() * xyRatio);
        bitmap = Bitmap.createScaledBitmap(
            bitmap, newWidth, newDimensionXorY, true);
    }
    return bitmap;
}

答案 9 :(得分：3)

  public Bitmap scaleBitmap(Bitmap mBitmap) {
        int ScaleSize = 250;//max Height or width to Scale
        int width = mBitmap.getWidth();
        int height = mBitmap.getHeight();
        float excessSizeRatio = width > height ? width / ScaleSize : height / ScaleSize;
         Bitmap bitmap = Bitmap.createBitmap(
                mBitmap, 0, 0,(int) (width/excessSizeRatio),(int) (height/excessSizeRatio));
        //mBitmap.recycle(); if you are not using mBitmap Obj
        return bitmap;
    }

答案 10 :(得分：3)

public static Bitmap resizeBitmapByScale(
            Bitmap bitmap, float scale, boolean recycle) {
        int width = Math.round(bitmap.getWidth() * scale);
        int height = Math.round(bitmap.getHeight() * scale);
        if (width == bitmap.getWidth()
                && height == bitmap.getHeight()) return bitmap;
        Bitmap target = Bitmap.createBitmap(width, height, getConfig(bitmap));
        Canvas canvas = new Canvas(target);
        canvas.scale(scale, scale);
        Paint paint = new Paint(Paint.FILTER_BITMAP_FLAG | Paint.DITHER_FLAG);
        canvas.drawBitmap(bitmap, 0, 0, paint);
        if (recycle) bitmap.recycle();
        return target;
    }
    private static Bitmap.Config getConfig(Bitmap bitmap) {
        Bitmap.Config config = bitmap.getConfig();
        if (config == null) {
            config = Bitmap.Config.ARGB_8888;
        }
        return config;
    }

答案 11 :(得分：2)

根据任何显示尺寸调整位图大小

public Bitmap bitmapResize(Bitmap imageBitmap) {

    Bitmap bitmap = imageBitmap;
    float heightbmp = bitmap.getHeight();
    float widthbmp = bitmap.getWidth();

    // Get Screen width
    DisplayMetrics displaymetrics = new DisplayMetrics();
    this.getWindowManager().getDefaultDisplay().getMetrics(displaymetrics);
    float height = displaymetrics.heightPixels / 3;
    float width = displaymetrics.widthPixels / 3;

    int convertHeight = (int) hight, convertWidth = (int) width;

    // higher
    if (heightbmp > height) {
        convertHeight = (int) height - 20;
        bitmap = Bitmap.createScaledBitmap(bitmap, convertWidth,
                convertHighet, true);
    }

    // wider
    if (widthbmp > width) {
        convertWidth = (int) width - 20;
        bitmap = Bitmap.createScaledBitmap(bitmap, convertWidth,
                convertHeight, true);
    }

    return bitmap;
}

答案 12 :(得分：1)

从API 19开始，存在Bitmap setWidth（int width）和setHeight（int height）。 http://developer.android.com/reference/android/graphics/Bitmap.html

答案 13 :(得分：1)

保持长宽比，

  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;
    }
}

答案 14 :(得分：0)

/**
 * Kotlin method for Bitmap scaling
 * @param bitmap the bitmap to be scaled
 * @param pixel  the target pixel size
 * @param width  the width
 * @param height the height
 * @param max    the max(height, width)
 * @return the scaled bitmap
 */
fun scaleBitmap(bitmap:Bitmap, pixel:Float, width:Int, height:Int, max:Int):Bitmap {
    val scale = px / max
    val h = Math.round(scale * height)
    val w = Math.round(scale * width)
    return Bitmap.createScaledBitmap(bitmap, w, h, true)
  }

答案 15 :(得分：0)

尽管接受的答案是正确的，但它不会通过保持相同的纵横比来调整Bitmap的大小。如果您正在寻找一种通过保持相同的宽高比来调整Bitmap大小的方法，则可以使用以下实用程序功能。 this link中提供了用法的详细信息和功能说明。

public static Bitmap resizeBitmap(Bitmap source, int maxLength) {
       try {
           if (source.getHeight() >= source.getWidth()) {
               int targetHeight = maxLength;
               if (source.getHeight() <= targetHeight) { // if image already smaller than the required height
                   return source;
               }

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

               Bitmap result = Bitmap.createScaledBitmap(source, targetWidth, targetHeight, false);
               if (result != source) {
               }
               return result;
           } else {
               int targetWidth = maxLength;

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

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

               Bitmap result = Bitmap.createScaledBitmap(source, targetWidth, targetHeight, false);
               if (result != source) {
               }
               return result;

           }
       }
       catch (Exception e)
       {
           return source;
       }
   }

答案 16 :(得分：0)

虽然前面的答案确实缩放了图像并注意了纵横比，但应该完成重采样本身，以免出现锯齿。处理规模是正确修正论点的问题。有很多关于标准缩放调用输出图像质量的评论。要保持图像质量，应使用标准调用：

Bitmap resizedBitmap = Bitmap.createScaledBitmap(originalBitmap, newWidth, newHeight, true);

将最后一个参数设置为 true 因为它会对重采样进行双线性过滤以防止混叠。在此处阅读有关别名的更多信息：https://en.wikipedia.org/wiki/Aliasing

来自安卓文档：

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


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

filter : boolean, 缩放位图时是否使用双线性过滤。如果这是真的，那么在缩放时将使用双线性过滤，以降低性能为代价获得更好的图像质量。如果这是错误的，则使用最近邻缩放代替，这将具有更差的图像质量但速度更快。推荐的默认设置是将过滤器设置为“true”，因为双线性过滤的成本通常很小，而且图像质量的改进非常显着。

答案 17 :(得分：0)

* 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);
        }
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