iPhone - 多个 OpenGL (CAEaglelayer) View 的屏幕截图

Question

我正在开发绘画应用程序，并引用 GLPaint 应用程序。在此应用程序中，有两个 Canvas View ，一个 View 从左向右移动(动画)，另一个 View 用作背景 View (如图所示)。

我正在使用 CAEAGLLayer 在两个 View 中填充颜色(使用子类化技术)。它正在按预期工作。现在我必须截取完整 View (轮廓和两个 OpenGL View )的屏幕截图，但我只获取一个 View (移动 View 或背景 View )的屏幕截图。与屏幕截图相关的代码与两个 View 相关联，但一次仅保存一个 View 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; 
}

有什么方法可以合并两个 CAEaglelayer View 的内容吗？

请帮忙。

非常感谢。

Answer 1

您可以单独创建每个 View 的屏幕截图，然后将它们组合起来，如下所示:

UIGraphicsBeginImageContext(canvasSize);

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

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

您应该使用适当的canvasSize和框架来绘制每个生成的UIImage，这只是您如何做到这一点的示例