iPhone - 多个OpenGL（CAEaglelayer）视图的屏幕截图

Question

我正在从GLPaint应用程序中引用绘画应用程序。在这个应用程序中有两个画布视图，一个视图从左到右（动画），其他视图用作背景视图（如图所示）。

我使用CAEAGLLayer用于（使用子类技术）在两个视图中填充的颜色。它按预期工作。现在我必须截取完整的视图（大纲和两个OpenGL视图）的截图，但我只截取了一个视图（移动视图或背景视图）。与屏幕截图相关的代码与两个视图相关联，但一次只保存一个视图的内容。

截图的代码片段如下。

- (UIImage*)snapshot:(UIView*)eaglview{ 

GLint backingWidth, backingHeight; 

// 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, &backingWidth); 
glGetRenderbufferParameterivOES(GL_RENDERBUFFER_OES, GL_RENDERBUFFER_HEIGHT_OES, &backingHeight); 
NSInteger x = 0, y = 0, width = backingWidth, height = backingHeight; 
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; 
} 

有什么办法可以将两个CAEaglelayer视图的内容组合起来吗？

请帮忙。

非常感谢。

Answer 1

您可以创建由单独的每个视图的屏幕截图，然后按如下结合他们：

UIGraphicsBeginImageContext(canvasSize); 

[openGLImage1 drawInRect:CGRectMake(0, 0, canvasSize.width, canvasSize.height)]; 
[openGLImage2 drawInRect:CGRectMake(0, 0, canvasSize.width, canvasSize.height)]; 

UIImage *resultingImage = UIGraphicsGetImageFromCurrentImageContext(); 
UIGraphicsEndImageContext(); 

你应该使用合适的canvasSize和帧绘制每个产生的UIImage，它仅仅是一个的，你怎么能这样做样本它

Answer 2

请参阅here一个更好的方法来做到这一点。它基本上允许您捕获一个包含所有OpenGL（和其他）视图的较大视图合并为一个完整的截图，这与您在屏幕上看到的截图完全相同。