Question

我正在寻找以下问题的解决方案：如何将Bitmap的大小更改为固定大小（例如512x128）。必须保留位图内容的宽高比。

我认为它应该是这样的：

创建一个空的512x128位图
缩小原始位图以适应512x128像素并保持纵横比
将缩放复制到空位图（居中）

实现这一目标的最简单方法是什么？

所有这一切的原因是，当图像的宽高比不同时，GridView会混淆布局。这是一个截图（除最后一个之外的所有图像都具有4：1的宽高比）：

Answer 1

尝试此操作，计算比率，然后重新缩放。

private Bitmap scaleBitmap(Bitmap bm) {
    int width = bm.getWidth();
    int height = bm.getHeight();

    Log.v("Pictures", "Width and height are " + width + "--" + height);

    if (width > height) {
        // landscape
        float ratio = (float) width / maxWidth;
        width = maxWidth;
        height = (int)(height / ratio);
    } else if (height > width) {
        // portrait
        float ratio = (float) height / maxHeight;
        height = maxHeight;
        width = (int)(width / ratio);
    } else {
        // square
        height = maxHeight;
        width = maxWidth;
    }

    Log.v("Pictures", "after scaling Width and height are " + width + "--" + height);

    bm = Bitmap.createScaledBitmap(bm, width, height, true);
    return bm;
}

Answer 2

Coen Damen的回答并不总是尊重Max Height和Max Width。这是一个答案：

 private static Bitmap resize(Bitmap image, int maxWidth, int maxHeight) {
    if (maxHeight > 0 && maxWidth > 0) {
        int width = image.getWidth();
        int height = image.getHeight();
        float ratioBitmap = (float) width / (float) height;
        float ratioMax = (float) maxWidth / (float) maxHeight;

        int finalWidth = maxWidth;
        int finalHeight = maxHeight;
        if (ratioMax > 1) {
            finalWidth = (int) ((float)maxHeight * ratioBitmap);
        } else {
            finalHeight = (int) ((float)maxWidth / ratioBitmap);
        }
        image = Bitmap.createScaledBitmap(image, finalWidth, finalHeight, true);
        return image;
    } else {
        return image;
    }
}

Answer 3

我在我的项目中多次偶然发现同样的问题，每次由于时间不够（和懒惰），我会对一个不太理想的解决方案感到满意。但最近我找到了一些时间来打击这个特殊问题。这是我的解决方案，我希望它有助于某人下线...

Bitmap scaleDownLargeImageWithAspectRatio(Bitmap image)
            {
                int imaheVerticalAspectRatio,imageHorizontalAspectRatio;
                float bestFitScalingFactor=0;
                float percesionValue=(float) 0.2;

                //getAspect Ratio of Image
                int imageHeight=(int) (Math.ceil((double) image.getHeight()/100)*100);
                int imageWidth=(int) (Math.ceil((double) image.getWidth()/100)*100);
                int GCD=BigInteger.valueOf(imageHeight).gcd(BigInteger.valueOf(imageWidth)).intValue();
                imaheVerticalAspectRatio=imageHeight/GCD;
                imageHorizontalAspectRatio=imageWidth/GCD;
                Log.i("scaleDownLargeImageWIthAspectRatio","Image Dimensions(W:H): "+imageWidth+":"+imageHeight);
                Log.i("scaleDownLargeImageWIthAspectRatio","Image AspectRatio(W:H): "+imageHorizontalAspectRatio+":"+imaheVerticalAspectRatio);

                //getContainer Dimensions
                int displayWidth = getWindowManager().getDefaultDisplay().getWidth();
                int displayHeight = getWindowManager().getDefaultDisplay().getHeight();
               //I wanted to show the image to fit the entire device, as a best case. So my ccontainer dimensions were displayWidth & displayHeight. For your case, you will need to fetch container dimensions at run time or you can pass static values to these two parameters 

                int leftMargin = 0;
                int rightMargin = 0;
                int topMargin = 0;
                int bottomMargin = 0;
                int containerWidth = displayWidth - (leftMargin + rightMargin);
                int containerHeight = displayHeight - (topMargin + bottomMargin);
                Log.i("scaleDownLargeImageWIthAspectRatio","Container dimensions(W:H): "+containerWidth+":"+containerHeight);

                //iterate to get bestFitScaleFactor per constraints
                while((imageHorizontalAspectRatio*bestFitScalingFactor <= containerWidth) && 
                        (imaheVerticalAspectRatio*bestFitScalingFactor<= containerHeight))
                {
                    bestFitScalingFactor+=percesionValue;
                }

                //return bestFit bitmap
                int bestFitHeight=(int) (imaheVerticalAspectRatio*bestFitScalingFactor);
                int bestFitWidth=(int) (imageHorizontalAspectRatio*bestFitScalingFactor);
                Log.i("scaleDownLargeImageWIthAspectRatio","bestFitScalingFactor: "+bestFitScalingFactor);
                Log.i("scaleDownLargeImageWIthAspectRatio","bestFitOutPutDimesions(W:H): "+bestFitWidth+":"+bestFitHeight);
                image=Bitmap.createScaledBitmap(image, bestFitWidth,bestFitHeight, true);

                //Position the bitmap centre of the container
                int leftPadding=(containerWidth-image.getWidth())/2;
                int topPadding=(containerHeight-image.getHeight())/2;
                Bitmap backDrop=Bitmap.createBitmap(containerWidth, containerHeight, Bitmap.Config.RGB_565);
                Canvas can = new Canvas(backDrop);
                can.drawBitmap(image, leftPadding, topPadding, null);

                return backDrop;
            }

Answer 4

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

并确保从dstWidth和dstHeight获取src.getWidth()*scale和src.getHeight()*scale，其中scale是您需要确定的值确保缩放的位图适合512x128。

Answer 5

我认为@Coen的答案不是此问题的正确解决方案。我还需要这样的方法，但我想对图像进行平方。

这是我对方形图像的解决方案；

public static Bitmap resizeBitmapImageForFitSquare(Bitmap image, int maxResolution) {

    if (maxResolution <= 0)
        return image;

    int width = image.getWidth();
    int height = image.getHeight();
    float ratio = (width >= height) ? (float)maxResolution/width :(float)maxResolution/height;

    int finalWidth = (int) ((float)width * ratio);
    int finalHeight = (int) ((float)height * ratio);

    image = Bitmap.createScaledBitmap(image, finalWidth, finalHeight, true);

    if (image.getWidth() == image.getHeight())
        return image;
    else {
        //fit height and width
        int left = 0;
        int top = 0;

        if(image.getWidth() != maxResolution)
            left = (maxResolution - image.getWidth()) / 2;

        if(image.getHeight() != maxResolution)
            top = (maxResolution - image.getHeight()) / 2;

        Bitmap bitmap = Bitmap.createBitmap(maxResolution, maxResolution, Bitmap.Config.ARGB_8888);
        Canvas canvas = new Canvas(bitmap);
        canvas.drawBitmap(image, left, top, null);
        canvas.save();
        canvas.restore();

        return  bitmap;
    }
}

将位图大小调整为固定值但不更改宽高比

5 个答案: