[英]OpenGL ES: Screenshot size is different in retina and non-retina devices
我是opengl es 2.0开发的新手。 我从屏幕截图中获取的UIImage在非视网膜设备(iphone 4和ipad)上看起来不错,但是当我从视网膜设备上获取屏幕截图时,它似乎放大了。 这是我使用的代码。
-(UIImage *) glToUIImage {
CGSize size = self.view.frame.size;
// the reason I set the height and width up-side-down is because my
// screenshot captured in landscape mode.
int image_height = (int)size.width;
int image_width = (int)size.height;
NSInteger myDataLength = image_width * image_height * 4;
// allocate array and read pixels into it.
GLubyte *buffer = (GLubyte *) malloc(myDataLength);
glReadPixels(0, 0, image_width, image_height, 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 < image_height; y++)
{
for(int x = 0; x < image_width * 4; x++)
{
buffer2[(image_height - 1 - y) * image_width * 4 + x] = buffer[y * 4 * image_width + x];
}
}
// make data provider with data.
CGDataProviderRef provider = CGDataProviderCreateWithData(NULL, buffer2, myDataLength, NULL);
// prep the ingredients
int bitsPerComponent = 8;
int bitsPerPixel = 32;
int bytesPerRow = 4 * image_width;
CGColorSpaceRef colorSpaceRef = CGColorSpaceCreateDeviceRGB();
CGBitmapInfo bitmapInfo = kCGBitmapByteOrderDefault;
CGColorRenderingIntent renderingIntent = kCGRenderingIntentDefault;
// make the cgimage
CGImageRef imageRef = CGImageCreate(image_width, image_height, bitsPerComponent, bitsPerPixel, bytesPerRow, colorSpaceRef, bitmapInfo, provider, NULL, NO, renderingIntent);
// then make the uiimage from that
UIImage *myImage = [UIImage imageWithCGImage:imageRef];
return myImage;
}
// screenshot function, combined my opengl image with background image and
// saved into Photos.
-(UIImage*)screenshot
{
UIImage *image = [self glToUIImage];
CGRect pos = CGRectMake(0, 0, image.size.width, image.size.height);
UIGraphicsBeginImageContext(image.size);
[image drawInRect:pos];
[self.background.image drawInRect:pos];
UIImage* final = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
// final picture I saved into Photos.
return final;
}
功能正在起作用,但是opengl图像仅显示了视网膜设备中的一部分,如何解决此问题。 谢谢 !!!
您的代码假定视图大小等于像素,但不是。 是要点。 您需要转换为每个设备的实际像素大小。 UIScreen为此具有scale属性。
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