[英]Screenshot of OpenGL ES content for Paint app
我正在为iphone绘制应用程序。 在我的代码中,我使用的imageView包含轮廓图像,在该图像上放置CAEAGLLayer可以在轮廓图像中填充颜色。 现在,我使用功能拍摄OpenGL ES [CAEAGLLayer]渲染内容的屏幕截图:
- (UIImage*)snapshot:(UIView*)eaglview{
GLint backingWidth1, backingHeight1;
// Bind the color renderbuffer used to render the OpenGL ES view
// If your application only creates a single color renderbuffer which is already bound at this point,
// this call is redundant, but it is needed if you're dealing with multiple renderbuffers.
// Note, replace "_colorRenderbuffer" with the actual name of the renderbuffer object defined in your class.
glBindRenderbufferOES(GL_RENDERBUFFER_OES, viewRenderbuffer);
// Get the size of the backing CAEAGLLayer
glGetRenderbufferParameterivOES(GL_RENDERBUFFER_OES, GL_RENDERBUFFER_WIDTH_OES, &backingWidth1);
glGetRenderbufferParameterivOES(GL_RENDERBUFFER_OES, GL_RENDERBUFFER_HEIGHT_OES, &backingHeight1);
NSInteger x = 0, y = 0, width = backingWidth1, height = backingHeight1;
NSInteger dataLength = width * height * 4;
GLubyte *data = (GLubyte*)malloc(dataLength * sizeof(GLubyte));
// Read pixel data from the framebuffer
glPixelStorei(GL_PACK_ALIGNMENT, 4);
glReadPixels(x, y, width, height, GL_RGBA, GL_UNSIGNED_BYTE, data);
// Create a CGImage with the pixel data
// If your OpenGL ES content is opaque, use kCGImageAlphaNoneSkipLast to ignore the alpha channel
// otherwise, use kCGImageAlphaPremultipliedLast
CGDataProviderRef ref = CGDataProviderCreateWithData(NULL, data, dataLength, NULL);
CGColorSpaceRef colorspace = CGColorSpaceCreateDeviceRGB();
CGImageRef iref = CGImageCreate(width, height, 8, 32, width * 4, colorspace, kCGBitmapByteOrder32Big | kCGImageAlphaPremultipliedLast,
ref, NULL, true, kCGRenderingIntentDefault);
// OpenGL ES measures data in PIXELS
// Create a graphics context with the target size measured in POINTS
NSInteger widthInPoints, heightInPoints;
if (NULL != UIGraphicsBeginImageContextWithOptions) {
// On iOS 4 and later, use UIGraphicsBeginImageContextWithOptions to take the scale into consideration
// Set the scale parameter to your OpenGL ES view's contentScaleFactor
// so that you get a high-resolution snapshot when its value is greater than 1.0
CGFloat scale = eaglview.contentScaleFactor;
widthInPoints = width / scale;
heightInPoints = height / scale;
UIGraphicsBeginImageContextWithOptions(CGSizeMake(widthInPoints, heightInPoints), NO, scale);
}
else {
// On iOS prior to 4, fall back to use UIGraphicsBeginImageContext
widthInPoints = width;
heightInPoints = height;
UIGraphicsBeginImageContext(CGSizeMake(widthInPoints, heightInPoints));
}
CGContextRef cgcontext = UIGraphicsGetCurrentContext();
// UIKit coordinate system is upside down to GL/Quartz coordinate system
// Flip the CGImage by rendering it to the flipped bitmap context
// The size of the destination area is measured in POINTS
CGContextSetBlendMode(cgcontext, kCGBlendModeCopy);
CGContextDrawImage(cgcontext, CGRectMake(0.0, 0.0, widthInPoints, heightInPoints), iref);
// Retrieve the UIImage from the current context
UIImage *image = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
// Clean up
free(data);
CFRelease(ref);
CFRelease(colorspace);
CGImageRelease(iref);
return image;}
使用功能将此屏幕快照与轮廓图像结合起来:
- (void)Combine:(UIImage *)Back{
UIImage *Front =backgroundImageView.image;
//UIGraphicsBeginImageContext(Back.size);
UIGraphicsBeginImageContext(CGSizeMake(640,960));
// Draw image1
[Back drawInRect:CGRectMake(0, 0, Back.size.width*2, Back.size.height*2)];
// Draw image2
[Front drawInRect:CGRectMake(0, 0, Front.size.width*2, Front.size.height*2)];
UIImage *resultingImage = UIGraphicsGetImageFromCurrentImageContext();
UIImageWriteToSavedPhotosAlbum(resultingImage, nil, nil, nil);
UIGraphicsEndImageContext();
}
使用功能将此图像保存到相册
-(void)captureToPhotoAlbum {
[self Combine:[self snapshot:self]];
UIAlertView *alert = [[UIAlertView alloc] initWithTitle:@"Success" message:@"Image saved to Photo Album" delegate:nil cancelButtonTitle:@"OK" otherButtonTitles:nil];
[alert show];
[alert release]; }
上述代码可以正常工作,但屏幕截图的图像质量较差。 画笔的轮廓上有一个灰色轮廓。 我上传了我的应用的屏幕截图,其中包含opengles内容和UIImage的组合。
有没有办法获取opengles-CAEaglelayer内容的视网膜显示屏幕截图。
先感谢您!
我不认为解决方案是您在这里遇到的问题。 如果您在图形出现在屏幕上时没有看到灰色的轮廓,则很可能是在保存过程中观察到压缩伪影。 您的图像可能被保存为较低质量的JPEG图像,其中的伪像将出现在尖锐的边缘上,例如图形中的那些边缘。
要解决此问题,Ben Weiss 在此处的答案提供了以下代码,用于强制将图像以PNG格式保存到照片库中:
UIImage* im = [UIImage imageWithCGImage:myCGRef]; // make image from CGRef
NSData* imdata = UIImagePNGRepresentation ( im ); // get PNG representation
UIImage* im2 = [UIImage imageWithData:imdata]; // wrap UIImage around PNG representation
UIImageWriteToSavedPhotosAlbum(im2, nil, nil, nil); // save to photo album
尽管这可能是在这里解决问题的最简单方法,但是您也可以尝试使用多重采样抗锯齿功能,如Apple在iOS的OpenGL ES编程指南的“ 使用多重采样提高图像质量 ”部分中所述。 根据您对填充率的限制,MSAA可能会导致应用程序速度稍有下降。
创建CG位图上下文时,您正在使用kCGImageAlphaPremultipliedLast。 尽管看不到您的OpenGL代码,但对我来说,您的OpenGL上下文似乎无法渲染预乘的alpha。 不幸的是,IIRC,无法在iOS上创建未预乘的CG位图上下文(它将使用kCGImageAlphaLast,但我认为这只会使创建调用失败),因此您可能需要在两者之间手动乘以数据从OpenGL获取它并制作CG上下文。
另一方面,您的OpenGL上下文是否具有alpha通道是有原因的吗? 您能否将其设为不透明白色,然后使用kCGImageAlphaNoneSkipLast?
声明:本站的技术帖子网页,遵循CC BY-SA 4.0协议,如果您需要转载,请注明本站网址或者原文地址。任何问题请咨询:yoyou2525@163.com.