ios - 具有内存映射原始数据的 UIImage (CGImage)

Question

有没有一种方法可以在 iOS 中将原始图像数据存储和加载到磁盘上，以节省解压时间和内存并减少应用程序的脏内存占用？

保罗·哈达德已hinting to something like this我知道这项技术用于 efficient game texture loading with OpenGL .

我的用例是用户提供的全屏墙纸始终显示在背景中。目前我将它保存为 PNG 并在应用程序启动期间加载它。这会浪费内存和 CPU 来解压缩图像。我想保存图像，然后将其作为内存映射文件加载。有没有办法在 CoreGraphics/UIKit 领域实现这一目标？

Answer 1

我用它来实时保存视频缓冲区的切片

 -(void)captureOutput:(AVCaptureOutput *)captureOutput didOutputSampleBuffer:(CMSampleBufferRef)sampleBuffer  fromConnection:(AVCaptureConnection *)connection
{

  CVImageBufferRef imageBuffer = CMSampleBufferGetImageBuffer(sampleBuffer);
  CVPixelBufferLockBaseAddress(imageBuffer,0);
  bytesPerRow = CVPixelBufferGetBytesPerRow(imageBuffer);
  void *baseAddress = CVPixelBufferGetBaseAddress(imageBuffer);

  size_t sliceSize = bytesPerRow*sliceWidth*sizeof(char);
  int slicePos= bytesPerRow*sliceStart*sizeof(char);
  NSData *rawFrame = [NSData dataWithBytes:(void*)baseAddress+slicePos length:sliceSize];

  inputPath = [NSString stringWithFormat:@"%@%@%d", NSTemporaryDirectory(), @"slice",step];
  [[NSData dataWithData:rawFrame] writeToFile:inputPath atomically:NO];
}

然后我用

读回来

-(void)readSlice
{
  //read slice i
  NSString *filePath = [NSString stringWithFormat:@"%@%@%d", NSTemporaryDirectory(), @"slice",i];            
  char* imgD= (char*)malloc(sliceSize);
  [[NSData dataWithContentsOfFile:filePath] getBytes:imgD];
  CGContextRef context = CGBitmapContextCreate(imgD, sliceHeight,sliceWidth, 8, bytesPerRad, colorSpace, kCGBitmapByteOrder32Little | kCGImageAlphaPremultipliedFirst);
  CGImageRef quartzImage = CGBitmapContextCreateImage(context);
  CGContextRelease(context);
  free(imgD);
  //do something with quartzImage
}