此函数的目的是从openGL图像返回UIImage。它被转换为CG图像的原因是openGL和UIKit元素可以在彼此之上呈现,这在另一个函数中处理。
奇怪的是,当应用程序在模拟器中运行时,一切正常。但是,在多个不同的iPad上测试应用程序后,在drawGlToImage
上调用self
方法时,应用程序崩溃时出现EXC_BAD_ACCESS代码= 1错误。有谁知道我在这做什么导致这个?我已经读过UIGraphicsBeginImageContext()
曾经遇到线程安全问题,但似乎在iOS 4中修复了这个问题。
- (UIImage *)drawGlToImage
{
self.context = [EAGLContext currentContext];
[EAGLContext setCurrentContext:self.context];
UIGraphicsBeginImageContext(self.view.frame.size);
unsigned char buffer[1024 * 768 * 4];
NSInteger dataSize = 1024 * 768 * 4;
CGContextRef currentContext = UIGraphicsGetCurrentContext();
UIGraphicsPushContext(currentContext);
glReadPixels(0, 0, 1024, 768, GL_RGBA, GL_UNSIGNED_BYTE, &buffer);
//flip the image
GLubyte *flippedBuffer = (GLubyte *) malloc(dataSize);
for(int y = 0; y <768; y++)
{
for(int x = 0; x <1024 * 4; x++)
{
if(buffer[y* 4 * 1024 + x]==0)
flippedBuffer[(767 - y) * 1024 * 4 + x]=1;
else
flippedBuffer[(767 - y) * 1024 * 4 + x] = buffer[y* 4 * 1024 + x];
}
}
CGDataProviderRef ref = CGDataProviderCreateWithData(NULL, flippedBuffer, 1024 * 768 * 4, NULL);
CGImageRef iref = CGImageCreate(1024,768,8,32,1024*4, CGColorSpaceCreateDeviceRGB(), kCGImageAlphaLast, ref, NULL, true, kCGRenderingIntentDefault);
CGContextScaleCTM(currentContext, 1.0, -1.0);
CGContextTranslateCTM(currentContext, 0, -self.view.frame.size.height);
UIGraphicsPopContext();
UIImage *image = [[UIImage alloc] initWithCGImage:iref];
UIGraphicsEndImageContext();
return image;
free(flippedBuffer);
UIGraphicsPopContext();
}
当按下某个按钮时,调用的方法会进行此分配,从而导致应用程序崩溃。
UIImage *glImage = [self drawGlToImage];
答案 0 :(得分:0)
我不确定您在哪个阶段调用此方法。但在调用任何OpenGL函数之前,您需要设置正确的OpenGL上下文。在Xcode模板中,就是这一行
[EAGLContext setCurrentContext:self.context];
答案 1 :(得分:0)
以下是用于解决问题的代码
- (UIImage *)drawGlToImage {
// Code borrowed and tweaked from:
// http://stackoverflow.com/questions/9881143/missing-part-of-the-image-when-taking-screenshot-while-supporting-retina-display
CGFloat scale = UIScreen.mainScreen.scale;
CGFloat xOffset = 40.0f;
CGFloat yOffset = -16.0f;
CGSize size = CGSizeMake((self.chart.frame.size.width) * scale,
self.chart.frame.size.height * scale);
//Create buffer for pixels
GLuint bufferLength = size.width * size.height * 4;
GLubyte* buffer = (GLubyte*)malloc(bufferLength);
//Read Pixels from OpenGL
glReadPixels(0.0f, 0.0f, size.width, size.height, GL_RGBA, GL_UNSIGNED_BYTE, buffer);
//Make data provider with data.
CGDataProviderRef provider = CGDataProviderCreateWithData(NULL, buffer, bufferLength, NULL);
//Configure image
int bitsPerComponent = 8;
int bitsPerPixel = 32;
int bytesPerRow = 4 * size.width;
CGColorSpaceRef colorSpaceRef = CGColorSpaceCreateDeviceRGB();
CGBitmapInfo bitmapInfo = kCGImageAlphaLast;
CGColorRenderingIntent renderingIntent = kCGRenderingIntentDefault;
CGImageRef iref = CGImageCreate(size.width, size.height, bitsPerComponent, bitsPerPixel, bytesPerRow, colorSpaceRef, bitmapInfo, provider, NULL, NO, renderingIntent);
uint32_t* pixels = (uint32_t*)malloc(bufferLength);
CGContextRef context = CGBitmapContextCreate(pixels, size.width, size.height, 8, size.width * 4, CGImageGetColorSpace(iref), kCGImageAlphaPremultipliedLast | kCGBitmapByteOrder32Big);
CGContextTranslateCTM(context, 0.0f, size.height);
CGContextScaleCTM(context, 1.0f, -1.0f);
// These numbers are a little magical.
CGContextDrawImage(context, CGRectMake(xOffset, yOffset, ((size.width - (6.0f * scale)) / scale) - (xOffset / 2), (size.height / scale) - (yOffset / 2)), iref);
UIImage *outputImage = [UIImage imageWithCGImage:CGBitmapContextCreateImage(context)];
//Dealloc
CGDataProviderRelease(provider);
CGImageRelease(iref);
CGContextRelease(context);
free(buffer);
free(pixels);
return outputImage;
}