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纵横比。
我觉得应该是这样的：
创建一个空的 512x128 位图
缩小原始位图以适应 512x128 像素，同时保持纵横比
将缩放后的位图复制到空位图（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，当图像的纵横比与另一个图像的纵横比不同时，GridView 会使布局混乱。这是一个屏幕截图（除了最后一张，所有图片的宽高比都是 4:1）：
【问题讨论】：
标签： android view bitmap scaling
试试这个，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;
}
【讨论】：
Coen Damen 的回答并不总是尊重最大高度和最大宽度。 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;
}
}
【讨论】：
我在我的项目中多次偶然发现同样的问题，每次由于时间不足（和懒惰），我都会对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解决这个特殊问题。这是我的解决方案，我希望它可以帮助某人。
Bitmap scaleDownLargeImageWithAspectRatio(Bitmap image)
{
int imageVerticalAspectRatio,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();
imageVerticalAspectRatio=imageHeight/GCD;
imageHorizontalAspectRatio=imageWidth/GCD;
Log.i("scaleDownLargeImageWIthAspectRatio","Image Dimensions(W:H): "+imageWidth+":"+imageHeight);
Log.i("scaleDownLargeImageWIthAspectRatio","Image AspectRatio(W:H): "+imageHorizontalAspectRatio+":"+imageVerticalAspectRatio);
//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) &&
(imageVerticalAspectRatio*bestFitScalingFactor<= containerHeight))
{
bestFitScalingFactor+=percesionValue;
}
//return bestFit bitmap
int bestFitHeight=(int) (imageVerticalAspectRatio*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;
}
【讨论】：
并确保dstWidth 和dstHeight 都是从src.getWidth()*scale 和src.getHeight()*scale 获得的，其中scale 是您需要确定的值，以确保缩放位图适合512x128。
【讨论】：
createScaledBitmap 不能解决我的问题。这就是我已经使用的。在示例中，最后一张图像已按这种方式缩放。
我认为@Coen 的答案不是这个问题的正确解决方案。我也需要这样的方法，但我想对图像进行平方。
这是我的方形图像解决方案；
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;
}
}
【讨论】：