如何从CGImageRef获取PNG base64编码

Question

i have CGImageRef object （var quartzImage）.如何将此对象转换为 Web 的 PNG 数据格式："data：image/png;base64，"+ base64 data image

我的代码：

- (void)captureOutput:(AVCaptureOutput *)captureOutput didOutputSampleBuffer:(CMSampleBufferRef)sampleBuffer fromConnection:(AVCaptureConnection *)connection {
    CVImageBufferRef imageBuffer = CMSampleBufferGetImageBuffer(sampleBuffer);
    CVPixelBufferLockBaseAddress(imageBuffer, 0);
    void *baseAddress = CVPixelBufferGetBaseAddressOfPlane(imageBuffer, 0);
    size_t bytesPerRow = CVPixelBufferGetBytesPerRow(imageBuffer);
    size_t width = CVPixelBufferGetWidth(imageBuffer);
    size_t height = CVPixelBufferGetHeight(imageBuffer);
    CGColorSpaceRef colorSpace = CGColorSpaceCreateDeviceRGB();
    CGContextRef context = CGBitmapContextCreate(baseAddress, width, height, 8, bytesPerRow, colorSpace, kCGBitmapByteOrder32Little | kCGImageAlphaPremultipliedFirst);
    CGImageRef quartzImage = CGBitmapContextCreateImage(context);
    CVPixelBufferUnlockBaseAddress(imageBuffer,0);
    CGContextRelease(context);
    CGColorSpaceRelease(colorSpace);
    NSLog(@"%@",quartzImage);
}

Answer 1

如果您已经有一个CGImageRef（代码中的名称为 quartzImage），则无需创建NSImage。直接创建NSBitmapImageRep。而且在任何情况下都不应使用lockFocus方法。这适用于应描绘到屏幕上的图像。因此，lockFocus通常会为视网膜屏幕创建分辨率为 72 dpi 和 144 dpi 的图像。或者您想使用屏幕属性为 Web 创建图像？试试这个：

NSBitmapImageRep *bitmapRep = [[NSBitmapImageRep alloc] initWithCGImage:quartzImage];
NSData *repData = [bitmapRep representationUsingType:NSPNGFileType] properties:nil];
NSString *base64String = [repData base64EncodedStringWithOptions:0];

这base64...方法在 OS X 10.9 之前不可用。在这种情况下，您应该使用base64Encoding

Answer 2

NSImage *image = [NSImage imageWithCGImage:imageRef];
[image lockFocus];
NSBitmapImageRep *bitmapRep = [[NSBitmapImageRep alloc] initWithFocusedViewRect:NSMakeRect(0, 0, image.size.width, image.size.height)];
[image unlockFocus];
NSData *imageData = [bitmapRep representationUsingType:NSPNGFileType properties:nil];;
NSString *base64String = [imageData base64EncodedStringWithOptions:0];