縮放圖像並重新計算（x，y）

Question

我有一個尺寸爲11900x3200的圖像和一個標記在（2745,2730）上的點。這個尺寸太大，無法在iPhone屏幕上顯示。我想將圖像縮小到3200x2000。如何計算新縮小圖像上的新（x，y）位置。

Answer 1

您可以使用基於比率的圖像縮放實現此目的。

這種方法，你可以得到正確的形象沒有pixalate。

float ori_height=image.size.height; 
float ori_width=image.size.width; 



    NSString *orientation=@""; 

    if (ori_height>ori_width) 
    { 
     orientation=@"PORTRAIT"; 
    } 

    if (ori_width>ori_height) 
    { 
     orientation=@"LANDSCAPE"; 
    } 


    if ([orientation isEqualToString:@"LANDSCAPE"]) 
    { 





     if (ori_height<300) 
     { 

      int height_ratio=ori_height/4; 
      int width_ratio=ori_width/4; 

      UIGraphicsBeginImageContext(CGSizeMake(width_ratio,height_ratio)); 




      UIImage *currentImage = [self imageWithImageSimple:image scaledToSize:CGSizeMake(width_ratio, height_ratio)]; 


     } 
     else 
     { 
      int height_ratio=ori_height/6; 
      int width_ratio=ori_width/6; 



      UIGraphicsBeginImageContext(CGSizeMake(width_ratio,height_ratio)); 


      UIImage *currentImage = [self imageWithImageSimple:image scaledToSize:CGSizeMake(width_ratio, height_ratio)]; 

     } 

    } 
    else if ([orientation isEqualToString:@"PORTRAIT"]) 
    { 
     //NSLog(@"portrait"); 
     if (ori_height<300) 
     { 
      ... 
     } 
     else 
     { 
      int height_ratio=ori_height/6; 
      int width_ratio=ori_width/6; 



      UIGraphicsBeginImageContext(CGSizeMake(width_ratio,height_ratio)); 


     UIImage *currentImage = [self imageWithImageSimple:image scaledToSize:CGSizeMake(width_ratio, height_ratio)]; 

      //[currentImage drawInRect: CGRectMake(0, 0, width_ratio, height_ratio)]; 

     } 
    } 



    UIGraphicsEndImageContext(); 

然後另一種方法

-(UIImage *)imageWithImageSimple:(UIImage*)image scaledToSize:(CGSize)newSize 
{ 

UIGraphicsBeginImageContext(newSize); 

[image drawInRect:CGRectMake(0,0,newSize.width,newSize.height)]; 

UIImage *newImage = UIGraphicsGetImageFromCurrentImageContext(); 

UIGraphicsEndImageContext(); 

return newImage; 
}