Question

我在每个单元格中都有一个UITableView，其中有3 EAGLView，用户可以在其中绘制一些内容（在apple GLPaint之后，我只是使用了PaintView类）例如）

我正在尝试将此3 EAGLView转换为3个不同的UIImage按钮压力事件，但生成的UIImages始终等于上次编辑的EAGLView

这是我正在使用的代码（从here复制）：

- (UIImage*)saveImageFromGLView:(UIView *)glView withName:(NSString *)name{

if(glCheckFramebufferStatusOES(GL_FRAMEBUFFER_OES) != GL_FRAMEBUFFER_COMPLETE_OES)
{
    /// This IS being activated with code 0
    NSLog(@"failed to make complete framebuffer object %x", glCheckFramebufferStatusOES(GL_FRAMEBUFFER_OES));
}

int s = 1;
UIScreen* screen = [ UIScreen mainScreen ];
if ( [ screen respondsToSelector:@selector(scale) ] )
    s = (int) [ screen scale ];

const int w = self.frame.size.width;
const int h = self.frame.size.height;
const NSInteger myDataLength = w * h * 4 * s * s;
// allocate array and read pixels into it.
GLubyte *buffer = (GLubyte *) malloc(myDataLength);
glReadPixels(0, 0, w*s, h*s, GL_RGBA, GL_UNSIGNED_BYTE, buffer);
// gl renders "upside down" so swap top to bottom into new array.
// there's gotta be a better way, but this works.
GLubyte *buffer2 = (GLubyte *) malloc(myDataLength);
for(int y = 0; y < h*s; y++)
{
    memcpy( buffer2 + (h*s - 1 - y) * w * 4 * s, buffer + (y * 4 * w * s), w * 4 * s );
}
free(buffer); // work with the flipped buffer, so get rid of the original one.

// make data provider with data.
CGDataProviderRef provider = CGDataProviderCreateWithData(NULL, buffer2, myDataLength, NULL);
// prep the ingredients
int bitsPerComponent = 8;
int bitsPerPixel = 32;
int bytesPerRow = 4 * w * s;
CGColorSpaceRef colorSpaceRef = CGColorSpaceCreateDeviceRGB();
CGBitmapInfo bitmapInfo = kCGBitmapByteOrderDefault;
CGColorRenderingIntent renderingIntent = kCGRenderingIntentDefault;
// make the cgimage
CGImageRef imageRef = CGImageCreate(w*s, h*s, bitsPerComponent, bitsPerPixel, bytesPerRow, colorSpaceRef, bitmapInfo, provider, NULL, NO, renderingIntent);
// then make the uiimage from that
UIImage *myImage = [ UIImage imageWithCGImage:imageRef scale:s orientation:UIImageOrientationUp ];

// Create path.
NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
NSString *filePath = [[paths objectAtIndex:0] stringByAppendingPathComponent:name];

// Save image.
[UIImagePNGRepresentation(myImage) writeToFile:filePath atomically:YES];

CGImageRelease( imageRef );
CGDataProviderRelease(provider);
CGColorSpaceRelease(colorSpaceRef);
free(buffer2);

return myImage;
}

我认为这是一个背景问题，我怎么能获得三个不同的图像？

Answer 1

假设您为这些视图using retained backing（否则glReadPixels()在您呈现到屏幕后不起作用），我的猜测是每个视图都有不同的OpenGL ES上下文视图。 glReadPixels()只会从当前活动的上下文中拉出，从而拉出最后一个视图。

在您阅读上述方法中的每个视图的上下文之前，您需要使用以下代码：

[EAGLContext setCurrentContext:context];

从您的OpenGL ES渲染UIView中提取上下文。您可能希望将该上下文设置为UIView子类的只读属性，然后更改上述方法以接受该子类。然后，您可以在使用glReadPixels()之前切换到适当的上下文。

作为附带问题，您不应该在上面使用glCheckFramebufferStatusOES()。这只属于你的帧缓冲区创建代码，在上面的方法中没有任何实际意义。

将多个EAGLView转换为UIImage

1 个答案: