Question

我正在为客户制作增强现实应用。 OpenGL和EAGL部分已在Unity 3D中完成，并在我的应用程序中实现为View。

我现在需要的是一个按钮，用于捕捉OpenGL内容的截图，这是最后面的视图。

我自己尝试编写它，但是当我点击一个带有指定IBAction的按钮时，它只能节省1/4的屏幕（左下角） - 尽管它会将其保存到相机胶卷。

所以基本上，我怎么能让它保存整个屏幕尺寸，而不是仅仅四分之一？

这是我的方法代码：

-(IBAction)tagBillede:(id)sender
{
    UIImage *outputImage = nil;

    CGRect s = CGRectMake(0, 0, 320, 480);            
    uint8_t *buffer = (uint8_t *) malloc(s.size.width * s.size.height * 4);

    if (!buffer) goto error;

    glReadPixels(0, 0, s.size.width, s.size.height, GL_RGBA, GL_UNSIGNED_BYTE, buffer);    

    CGDataProviderRef ref = CGDataProviderCreateWithData(NULL, buffer, s.size.width * s.size.height * 4, NULL);

    if (!ref) goto error;

    CGImageRef iref = CGImageCreate(s.size.width, s.size.height, 8, 32, s.size.width * 4, CGColorSpaceCreateDeviceRGB(), kCGBitmapByteOrderDefault, ref, NULL, true, kCGRenderingIntentDefault);

    if (!iref) goto error;        

    size_t width = CGImageGetWidth(iref);    
    size_t height = CGImageGetHeight(iref);    
    size_t length = width * height * 4;            
    uint32_t *pixels = (uint32_t *)malloc(length);

    if (!pixels) goto error;

    CGContextRef context = CGBitmapContextCreate(pixels, width, height, 8, width * 4,    
        CGImageGetColorSpace(iref), kCGImageAlphaNoneSkipFirst | kCGBitmapByteOrder32Big);

    if (!context) goto error;            

    CGAffineTransform transform = CGAffineTransformIdentity;    
    transform = CGAffineTransformMakeTranslation(0.0f, height);    
    transform = CGAffineTransformScale(transform, 1.0, -1.0);    
    CGContextConcatCTM(context, transform);            
    CGContextDrawImage(context, CGRectMake(0.0f, 0.0f, width, height), iref);         
    CGImageRef outputRef = CGBitmapContextCreateImage(context);

    if (!outputRef) goto error;

    outputImage = [UIImage imageWithCGImage: outputRef]; 

    if (!outputImage) goto error;    

    CGDataProviderRelease(ref);   
    CGImageRelease(iref);    
    CGContextRelease(context);    
    CGImageRelease(outputRef);
    free(pixels);
    free(buffer);

    UIImageWriteToSavedPhotosAlbum(outputImage, self, @selector(image: didFinishSavingWithError: contextInfo:), nil);
}

Answer 1

我怀疑您使用的是具有Retina显示屏的设备，即640x960。您需要考虑屏幕比例;在非Retina显示器上为1.0，在Retina显示器上为2.0。尝试初始化s，如下所示：

CGFloat scale = UIScreen.mainScreen.scale;
CGRect s = CGRectMake(0, 0, 320 * scale, 480 * scale);

Answer 2

如果设备是视网膜设备，您需要自己缩放opengl。实际上，您只需要捕获一半宽度和一半高度来指定左下角。

您需要将视网膜屏幕的宽度和高度加倍，但实际上，您应该将其乘以屏幕的比例：

CGFloat scale = [[UIScreen mainScreen] scale];
CGRect s = CGRectMake(0, 0, 320.0f * scale, 480.0f * scale);

Answer 3

以为我会发出声音，同时也会感激不尽：）

我现在让它像魅力一样工作，这是清理过的代码：

UIImage *outputImage = nil;

CGFloat scale = [[UIScreen mainScreen] scale];
CGRect s = CGRectMake(0, 0, 320.0f * scale, 480.0f * scale);            
uint8_t *buffer = (uint8_t *) malloc(s.size.width * s.size.height * 4);

glReadPixels(0, 0, s.size.width, s.size.height, GL_RGBA, GL_UNSIGNED_BYTE, buffer);    

CGDataProviderRef ref = CGDataProviderCreateWithData(NULL, buffer, s.size.width * s.size.height * 4, NULL);

CGImageRef iref = CGImageCreate(s.size.width, s.size.height, 8, 32, s.size.width * 4, CGColorSpaceCreateDeviceRGB(), kCGBitmapByteOrderDefault, ref, NULL, true, kCGRenderingIntentDefault);

size_t width = CGImageGetWidth(iref);    
size_t height = CGImageGetHeight(iref);    
size_t length = width * height * 4;            
uint32_t *pixels = (uint32_t *)malloc(length);

CGContextRef context = CGBitmapContextCreate(pixels, width, height, 8, width * 4,    
                                             CGImageGetColorSpace(iref), kCGImageAlphaNoneSkipFirst | kCGBitmapByteOrder32Big);           

CGAffineTransform transform = CGAffineTransformIdentity;    
transform = CGAffineTransformMakeTranslation(0.0f, height);    
transform = CGAffineTransformScale(transform, 1.0, -1.0);    
CGContextConcatCTM(context, transform);            
CGContextDrawImage(context, CGRectMake(0.0f, 0.0f, width, height), iref);         
CGImageRef outputRef = CGBitmapContextCreateImage(context);

outputImage = [UIImage imageWithCGImage: outputRef]; 

CGDataProviderRelease(ref);   
CGImageRelease(iref);    
CGContextRelease(context);    
CGImageRelease(outputRef);
free(pixels);
free(buffer);

UIImageWriteToSavedPhotosAlbum(outputImage, nil, nil, nil);

glReadPixels仅保存1/4屏幕大小的快照

3 个答案: