如何ReSize图像与良好的质量在iPhone [英] How to ReSize Image with Good Quality in iPhone

问题描述

我想在iPhone中创建一个照片库作为现有照片库。我在从照片库中选择的scrollviewer中添加图像。添加图像之前调整所选图像的大小，并将其设置为ImageView控制。但当我比较添加的图像质量与iPhone照片库图像质量，我的控制图像不好。如何带来质量和withou内存溢出问题。

I want to create a Photos Library as existing photo library in iPhone. I add image in scrollviewer which is chosen from Photo library. Before add image i resize the selected image and set it to ImageView Control.But when i compare to added image quality with iPhone Photo library image quality, my control image is not good. How to bring the quality and withou memory overflow issue.

-(UIImage*)imageWithImage:(UIImage*)image scaledToSize:(CGSize)newSize
{
    // Create a bitmap context.
    UIGraphicsBeginImageContext( newSize );
    [image drawInRect:CGRectMake(0,0,newSize.width,newSize.height)];
    UIImage* newImage = UIGraphicsGetImageFromCurrentImageContext();
    UIGraphicsEndImageContext();
    return newImage;

}

推荐答案

进入这个问题。我想你使用的是带有Retina显示屏的iPhone 4。即使你不是，你应该解释它。取代 UIGraphicsBeginImageContext（），请使用 UIGraphicsBeginImageContextWithOptions（）并使用 scale 属性 UIScreen 用于第三个参数。所有iOS设备都有scale属性，在iPhone 4上设置为2.0;

I ran into this issue also. I think you're using an iPhone 4 with Retina Display. Even if you're not, you should account for it. Instead of UIGraphicsBeginImageContext(), use UIGraphicsBeginImageContextWithOptions() and use the scale property of UIScreen for the third argument. All iOS devices have the scale property, on iPhone 4 it's set to 2.0; on the rest, as I write this, it's set to 1.0.

因此，你的代码，与这些变化，变成

So your code, with those changes, becomes

-(UIImage *)imageWithImage:(UIImage*)image scaledToSize:(CGSize)newSize
{
    // Create a bitmap context.
    UIGraphicsBeginImageContextWithOptions(newSize, YES, [UIScreen mainScreen].scale);
    [image drawInRect:CGRectMake(0,0,newSize.width,newSize.height)];
    UIImage* newImage = UIGraphicsGetImageFromCurrentImageContext();
    UIGraphicsEndImageContext();
    return newImage;

}

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