PHP缩略图图像按比例调整大小

$maxwidth = 120;
$maxheight = 150;

$img = imagecreatefromjpeg($jpgimage); 
//or imagecreatefrompng,imagecreatefromgif,etc. depending on user's uploaded file extension

$width = imagesx($img); //get width and height of original image
$height = imagesy($img);

//determine which side is the longest to use in calculating length of the shorter side,since the longest will be the max size for whichever side is longest.    
if ($height > $width) 
{   
$ratio = $maxheight / $height;  
$newheight = $maxheight;
$newwidth = $width * $ratio; 
}
else 
{
$ratio = $maxwidth / $width;   
$newwidth = $maxwidth;  
$newheight = $height * $ratio;   
}

//create new image resource to hold the resized image
$newimg = imagecreatetruecolor($newwidth,$newheight); 

$palsize = ImageColorsTotal($img);  //Get palette size for original image
for ($i = 0; $i < $palsize; $i++) //Assign color palette to new image
{ 
$colors = ImageColorsForIndex($img,$i);   
ImageColorAllocate($newimg,$colors['red'],$colors['green'],$colors['blue']);
} 

//copy original image into new image at new size.
imagecopyresized($newimg,$img,$newwidth,$newheight,$width,$height);

imagejpeg($newimg,$outputfile); //$output file is the path/filename where you wish to save the file.  
//Have to figure that one out yourself using whatever rules you want.  Can use imagegif() or imagepng() or whatever.

这将根据较长的一侧(宽度或高度)按比例缩小任何图像,以达到最大尺寸.它还会炸掉任何小于最大值的图像,您可以通过检查宽度和高度是否小于最大值来停止.因此,200×300图像将缩小至100×150,300×200图像将缩小至120×80.

嗯,你想要宽度总是120,所以它会改变一点,是的,它必须在像200×300的图像的情况下削减一些东西,因为它会缩小到120×180没有任何失真,或者它会必须将它缩小得更远,并将信箱装箱,但这应该让你开始很好.

Letterboxing这个例子只需要弄清楚在imagecopyresized()函数中开始绘制到新图像的正确x和y是什么.在像100×150这样的情况下,我认为X将是10,所以最终每侧有10px的空白区域为120×150. Letterboxing 120×80 X将为0但Y将为35,因此对于120×150,上下将有35px的空白区域.

你还想用$maxwidth,$maxheight而不是$newwidth,$newheight制作$newimg,但是imagecopyresized()仍然会使用两个$new值.

由于我很无聊而且没有别的事可做,这些改变会做到：

if ($height > $width) 
{   
$ratio = $maxheight / $height;  
$newheight = $maxheight;
$newwidth = $width * $ratio; 
$writex = round(($maxwidth - $newwidth) / 2);
$writey = 0;
{
else 
{
$ratio = $maxwidth / $width;   
$newwidth = $maxwidth;  
$newheight = $height * $ratio;   
$writex = 0;
$writey = round(($maxheight - $newheight) / 2);
}

$newimg = imagecreatetruecolor($maxwidth,$maxheight);

//Since you probably will want to set a color for the letter box do this
//Assign a color for the letterbox to the new image,//since this is the first call,for imagecolorallocate,it will set the background color
//in this case,black rgb(0,0)
imagecolorallocate($newimg,0);

//Loop Palette assignment stuff here

imagecopyresized($newimg,$writex,$writey,$height);

这应该工作,尚未尝试过.