iOS图片按原比例缩小算法(类似微信聊天图片)

<h3>ps:因为这段时间做聊天功能，基本已经稳定，剩下就是优化小细节，今天发现聊天发送的图片和微信图片差别略大，网上搜了一下没有搜到相关代码，都是按尺寸相等缩小或剪裁等，自己记录一下方便以后用上，</h3>

<h6>代码贴上：</h6>

+ (CGSize)neededSizeForPhoto:(CGSize*)bubbleSize {

//bubbleSize  原尺寸

CGFloat maxWidth = IPHONE_WIDTH * 0.46;  //限制最大宽度或高度

CGFloat imageViewW = bubbleSize.width/2; 
CGFloat imageViewH = bubbleSize.height/2;

CGFloat factor = 1.0f;

  if(imageViewW > imageViewH){  

     if(imageViewW > maxWidth){

      factor = maxWidth/imageViewW;
      imageViewW = imageViewW*factor;
      imageViewH = imageViewH*factor;

    }else{

        if(imageViewH > maxWidth){

           factor = maxWidth/imageViewH;
           imageViewW = MAX(imageViewW*factor,46.0);  //限制宽度不能超过46.0
           imageViewH = imageViewH*factor;
   
          }

     }

bubbleSize = CGSizeMake(imageViewW, imageViewH);

return bubbleSize;

}

<h6>效果：</h6>

1616684-15e3eec185fd9065.png