调整图像大小和保持宽高比以适合iPhone的算法

Question

我正在为iPhone应用程序创建一个Web服务来进行交互.

当我的客户端上传服务器端的图像时,我希望我的php脚本调整图像大小,同时保持纵横比,以便它适合iPhone屏幕.(即最长边<= 960,最短<= 640

我在JS中创建了一个模型,只是因为我发现它更容易快速完成.

我很确定,虽然我可能错了,但这不是最有效的方法.有人可以用更好的逻辑(尤其是开头的那个)或更接近这个的数学方法来纠正我吗？

var w = 960, h = 960, new_w, new_h;
if (w >= h && w > 960 || h >= w && h > 960 || w >= h && h > 640 || h >= w && w > 640) {
    if (w > h) {
        if (w>960) {
            new_w = 960;
            new_h = h*(new_w/w);
        }
        if (h>640) {
            new_h = 640;
            new_w = w*(new_h/h);
        }
    }
    else {
        if (h>960) {
            new_h = 960;
            new_w = w*(new_h/h);
        }
        if (w>640) {
            new_w = 640;
            new_h = h*(new_w/w);
        }
    }
}

Answer 1

也许稍微短一点的例程是:

// Calculate resize ratios for resizing 
float ratioW = targetWidth / oldWidth; 
float ratioH = targetHeight / oldHeight;

// smaller ratio will ensure that the image fits in the view
float ratio = ratioW < ratioH?ratioW:ratioH;

newWidth = oldWidth*ratio;
newHeight = oldHeight*ratio;

显然,如果比率> 1,那么它正在扩大,如果<1那么它正在缩小.

Answer 2

我认为以下内容应该给你这个想法.它不是任何特定的语言,而是类似C的伪代码.

shortSideMax = 640;
longSideMax = 960;
function Resize(image)
{
    if (image.width >= image.height)
    {
        if (image.width <= longSideMax && image.height <= shortSideMax)
            return image;  // no resizing required
        wRatio = longSideMax / image.width;
        hRatio = shortSideMax / image.height;
    }
    else
    {
        if (image.height <= longSideMax && image.width <= shortSideMax)
            return image; // no resizing required
        wRatio = shortSideMax / image.width;
        hRatio = longSideMax / image.height;
    }

    // hRatio and wRatio now have the scaling factors for height and width.
    // You want the smallest of the two to ensure that the resulting image
    // fits in the desired frame and maintains the aspect ratio.
    resizeRatio = Min(wRatio, hRatio);

    newHeight = image.Height * resizeRatio;
    newWidth = image.Width * resizeRatio;

    // Now call function to resize original image to [newWidth, newHeight]
    // and return the result.
}

此代码的效率或您拥有的代码不会成为问题.实际调整图像大小所需的时间将使进行几次比较,两次除法和两次乘法所花费的时间相形见绌.

这是一种"更加数学化"的方式吗？我想,因为它将你的四个案件分成两个.但方法基本相同.

Answer 3

下面,我知道保持比例的最简单方法.希望能帮助到你.

使用Javascript

function resize(width, height, maxWidth, maxHeight) {
    var ratio = Math.min(maxWidth / width, maxHeight / height);
    var newWidth = ratio * width;
    var newHeight = ratio * height;

    console.log(newWidth + ' ' + newHeight); // Test

    // Process resizing...
}

resize(1280, 1024, 600, 300);

PHP

function resize($width, $height, $maxWidth, $maxHeight) {
    $ratio = min(array($maxWidth / $width, $maxHeight / $height));
    $newWidth = $ratio * $width;
    $newHeight = $ratio * $height;

    echo $newWidth . ' ' . $newHeight; // Test

    // Process resizing...
}

resize(1600, 1280, 150, 150);