调整图像大小以适合边界框

Question

一个简单的问题，但由于某种原因，我今天无法解决这个问题。

我需要将图像调整到适合边框的最大可能尺寸，同时保持纵横比。

基本上我正在寻找填写此功能的代码：

void CalcNewDimensions(ref int w, ref int h, int MaxWidth, int MaxHeight);

w＆amp; h是原始高度和宽度（in）以及新的高度和宽度（out），MaxWidth和MaxHeight定义图像必须适合的边界框。

Answer 1

查找哪个更小：MaxWidth / w或MaxHeight / h 然后将w和h乘以该数字

<强>解释

您需要找到使图像适合的缩放系数。

要查找宽度的缩放系数s，则s必须为：     s * w = MaxWidth。 因此，缩放因子为MaxWidth / w。

同样适用于身高。

需要最大缩放（较小s）的那个是您必须缩放整个图像的因素。

Answer 2

根据Eric的建议，我会做这样的事情：

private static Size ExpandToBound(Size image, Size boundingBox)
{       
    double widthScale = 0, heightScale = 0;
    if (image.Width != 0)
        widthScale = (double)boundingBox.Width / (double)image.Width;
    if (image.Height != 0)
        heightScale = (double)boundingBox.Height / (double)image.Height;                

    double scale = Math.Min(widthScale, heightScale);

    Size result = new Size((int)(image.Width * scale), 
                        (int)(image.Height * scale));
    return result;
}

我可能在演员阵容上有点过分，但我只是想在计算中保持精确度。

Answer 3

试过沃伦先生的代码，但它没有产生可靠的结果。

例如，

ExpandToBound(new Size(640,480), new Size(66, 999)).Dump();
// {Width=66, Height=49}

ExpandToBound(new Size(640,480), new Size(999,50)).Dump();
// {Width=66, Height=50}

你可以看到，身高= 49，身高= 50。

这是我的（Warren先生代码的基础版本）没有差异和轻微的重构：

// Passing null for either maxWidth or maxHeight maintains aspect ratio while
//        the other non-null parameter is guaranteed to be constrained to
//        its maximum value.
//
//  Example: maxHeight = 50, maxWidth = null
//    Constrain the height to a maximum value of 50, respecting the aspect
//    ratio, to any width.
//
//  Example: maxHeight = 100, maxWidth = 90
//    Constrain the height to a maximum of 100 and width to a maximum of 90
//    whichever comes first.
//
private static Size ScaleSize( Size from, int? maxWidth, int? maxHeight )
{
   if ( !maxWidth.HasValue && !maxHeight.HasValue ) throw new ArgumentException( "At least one scale factor (toWidth or toHeight) must not be null." );
   if ( from.Height == 0 || from.Width == 0 ) throw new ArgumentException( "Cannot scale size from zero." );

   double? widthScale = null;
   double? heightScale = null;

   if ( maxWidth.HasValue )
   {
       widthScale = maxWidth.Value / (double)from.Width;
   }
   if ( maxHeight.HasValue )
   {
       heightScale = maxHeight.Value / (double)from.Height;
   }

   double scale = Math.Min( (double)(widthScale ?? heightScale),
                            (double)(heightScale ?? widthScale) );

   return new Size( (int)Math.Floor( from.Width * scale ), (int)Math.Ceiling( from.Height * scale ) );
}

Answer 4

要执行宽高比填充而不是宽高比，请使用较大的比例。也就是说，将Matt的代码从Math.Min更改为Math.Max。

（方面填充不会使边界框空，但可能会将某些图像放在边界之外，而方面适合不会使边界之外的任何图像留下，但可能会使某些边界框留空。）

Answer 5

以下代码可以产生更准确的结果：

    public static Size CalculateResizeToFit(Size imageSize, Size boxSize)
    {
        // TODO: Check for arguments (for null and <=0)
        var widthScale = boxSize.Width / (double)imageSize.Width;
        var heightScale = boxSize.Height / (double)imageSize.Height;
        var scale = Math.Min(widthScale, heightScale);
        return new Size(
            (int)Math.Round((imageSize.Width * scale)),
            (int)Math.Round((imageSize.Height * scale))
            );
    }

Answer 6

简单。 :)问题是找到一个需要乘以宽度和高度的因子。解决方案是尝试使用一个，如果不适合，请使用另一个。所以......

private float ScaleFactor(Rectangle outer, Rectangle inner)
{
    float factor = (float)outer.Height / (float)inner.Height;
    if ((float)inner.Width * factor > outer.Width) // Switch!
        factor = (float)outer.Width / (float)inner.Width;
    return factor;
}

将图片（pctRect）拟合到窗口（wndRect）这样的调用

float factor=ScaleFactor(wndRect, pctRect); // Outer, inner
RectangleF resultRect=new RectangleF(0,0,pctRect.Width*factor,pctRect.Height*Factor)

Answer 7

Python代码，但它可能会指向正确的方向：

def fit_within_box(box_width, box_height, width, height):
    """
    Returns a tuple (new_width, new_height) which has the property
    that it fits within box_width and box_height and has (close to)
    the same aspect ratio as the original size
    """
    new_width, new_height = width, height
    aspect_ratio = float(width) / float(height)

    if new_width > box_width:
        new_width = box_width
        new_height = int(new_width / aspect_ratio)

    if new_height > box_height:
        new_height = box_height
        new_width = int(new_height * aspect_ratio)

    return (new_width, new_height)

Answer 8

根据之前的答案，这是一个Javascript函数：

/**
* fitInBox
* Constrains a box (width x height) to fit in a containing box (maxWidth x maxHeight), preserving the aspect ratio
* @param width      width of the box to be resized
* @param height     height of the box to be resized
* @param maxWidth   width of the containing box
* @param maxHeight  height of the containing box
* @param expandable (Bool) if output size is bigger than input size, output is left unchanged (false) or expanded (true)
* @return           {width, height} of the resized box
*/
function fitInBox(width, height, maxWidth, maxHeight, expandable) {
    "use strict";

    var aspect = width / height,
        initWidth = width,
        initHeight = height;

    if (width > maxWidth || height < maxHeight) {
        width = maxWidth;
        height = Math.floor(width / aspect);
    }

    if (height > maxHeight || width < maxWidth) {
        height = maxHeight;
        width = Math.floor(height * aspect);
    }

    if (!!expandable === false && (width >= initWidth || height >= initHeight)) {
        width = initWidth;
        height = initHeight;
    }

    return {
        width: width,
        height: height
    };
}

Answer 9

我遇到了类似的问题，我发现它非常有用：article。据我所知，你需要调整图像大小？

Answer 10

用于此任务的Python代码基于Jason的答案，并针对通过img.shape传递的常规参数进行了升级和参数重排。

def fit_within_box(box_height, box_width, height, width):
    """
    Returns a tuple (new_width, new_height) which has the property
    that it fits within box_width and box_height and has (close to)
    the same aspect ratio as the original size
    """
    new_width, new_height = width, height
    aspect_ratio = float(width) / float(height)

    if new_width > box_width or new_height < box_height:
        new_width = box_width
        new_height = int(new_width / aspect_ratio)

    if new_height > box_height or new_width < box_width:
        new_height = box_height
        new_width = int(new_height * aspect_ratio)

    return new_height, new_width