组合多个 UIImageView 并保持分辨率

Question

我正在设计一个应用程序，用户可以将多个 UIImageView 一个一个地放置。当用户决定将其保存到相册时，我必须组合所有这些 UIImageView 并将其保存到照片库。在组合它们时，我需要保留它们的位置、分辨率、zorder。我尝试的方法是有一个父 UIView，它的作用就像一个容器。用户将所有 UIImageView 放入此 UIView 中。保存时，我截取 UIView 的屏幕截图并保存。尽管这种方法有效，但它并不能保留分辨率。最终图像的分辨率与父UIView尺寸的分辨率相同（宽度和高度均为300像素）。有办法保留分辨率吗？或者至少有更高的分辨率，例如高达 1024 x 768 像素？任何指针/代码示例将不胜感激！

Answer 1

如果 UIView 的大小高于您拥有的最大图像的大小，那么您正在做的保存 UIView 是一个非常好的主意，但情况几乎从未如此。
您所要做的就是创建一个与最大图像一样大的图形上下文 (CGContextRef)，按 z 顺序对图像进行排序，然后开始在那里绘制这些图像。
我会尝试用一些伪代码来帮助您：

-(UIImage *)mergeFlag{

UIImage * mergedImage = nil;

//In some pace you need to fill these values with the biggest width of all your images and the biggest height;
int Max_Width;
int Max_Height;

//Use here your image with the biggest Z-order.
CGImageRef image;

size_t cWitdh = Max_Width;
size_t cHeight = Max_Height;
size_t bitsPerComponent = 8;//If 8 isn't right you should use CGImageGetBitsPerComponent(image) with some image.
size_t bytesPerRow = 4 * Max_Width;// I use 4 assuming you have 8 Bits per component and you have 4 components (R,G,B,A) , if you have an image specifically, you can use CGImageGetBytesPerRow(image)

//Now we build a Context with those dimensions.
CGContextRef context = CGBitmapContextCreate(nil, cWitdh, cHeight, bitsPerComponent, bytesPerRow, CGColorSpaceCreateDeviceRGB(), CGImageGetBitmapInfo(image));

//The code of this cycle is to ilustrate what you have to do:
for(image in your Images ordered by z-Order)
{
    //The location where you draw your image on the context is not always the same location you have in your UIView, 
    //this could change and you need to calculate that position according to the scale between you images real size, and the size of the UIImage being show on the UIView.
    CGContextDrawImage(context, CGRectMake(currentImage.frame.origin.x, currentImage.frame.origin.y, CGImageGetWidth(currentImage), CGImageGetHeight(currentImage), currentImage);
}

CGImageRef mergeResult  = CGBitmapContextCreateImage(context);
mergedImage = [[UIImage alloc] initWithCGImage:tmp];
CGContextRelease(context);
CGImageRelease(mergeResult);
return mergedImage;}

希望它有帮助。