Iphone iOS如何高效地在cgimage上执行旋转(最多125帧)?
我有两个图像,我们称之为图像A和图像B。我正在尝试旋转和缩放图像A,并在图像B的顶部的特定位置绘制它 我使用以下功能和方法: 1.旋转并缩放我的图像 2.在特定位置将图像A绘制到图像B中 这段代码运行得很好,但速度相当慢,有没有改进的方法 旋转和缩放功能:Iphone iOS如何高效地在cgimage上执行旋转(最多125帧)?,iphone,objective-c,ios,uiimage,cgimage,Iphone,Objective C,Ios,Uiimage,Cgimage,我有两个图像,我们称之为图像A和图像B。我正在尝试旋转和缩放图像A,并在图像B的顶部的特定位置绘制它 我使用以下功能和方法: 1.旋转并缩放我的图像 2.在特定位置将图像A绘制到图像B中 这段代码运行得很好,但速度相当慢,有没有改进的方法 旋转和缩放功能: CGImageRef rotateAndScaleImageCreate(const CGImageRef cgImage, const CGFloat radians,const CGFloat scalefactor){ CGImageR
CGImageRef rotateAndScaleImageCreate(const CGImageRef cgImage, const CGFloat radians,const CGFloat scalefactor){
CGImageRef rotatedImageRef = NULL;
const CGFloat originalWidth = CGImageGetWidth(cgImage)*scalefactor;
const CGFloat originalHeight = CGImageGetHeight(cgImage)*scalefactor;
const CGRect imgRect = (CGRect){.origin.x = 0.0f, .origin.y = 0.0f, .size.width = originalWidth, .size.height = originalHeight};
const CGRect rotatedRect = CGRectApplyAffineTransform(imgRect, CGAffineTransformMakeRotation(radians));
/// Create an ARGB bitmap context
CGContextRef bmContext = NYXImageCreateARGBBitmapContext(rotatedRect.size.width, rotatedRect.size.height, 0);
if (!bmContext)
return nil;
/// Rotation happen here
CGContextTranslateCTM(bmContext, +(rotatedRect.size.width * 0.5f), +(rotatedRect.size.height * 0.5f));
CGContextRotateCTM(bmContext, radians);
/// Draw the image in the bitmap context
CGContextDrawImage(bmContext, (CGRect){.origin.x = -originalWidth * 0.5f, .origin.y = -originalHeight * 0.5f, .size.width = originalWidth, .size.height = originalHeight}, cgImage);
/// Create an image object from the context
rotatedImageRef = CGBitmapContextCreateImage(bmContext);
/// Cleanup
//CGImageRelease(rotatedImageRef);
CGContextRelease(bmContext);
return rotatedImageRef;
}
在另一个图像中的特定位置绘制图像的方法:
-(UIImage*) PositionImage:(CGImageRef)image backgroundImage:(CGImageRef)backgroundImage atPointX:(float)X pointY:(float)Y withScale:(float)scale andRotation:(float)rotation{
//////////////////////////////////////////
CGLayerRef layer;
CGImageRef resultImage;
CGContextRef context, layerContext;
void *bitmapData;
CGColorSpaceRef colorSpace;
CGSize canvasSize;
int bitmapByteCount;
int bitmapBytesPerRow;
//Get the background image
//UIImage * backgroundImg = [UIImage imageNamed:@"Mask-Inverted.png"];
//Initialize the canvas size!
canvasSize = CGSizeMake(480,640);//[backgroundImg size];
//
bitmapBytesPerRow = (canvasSize.width * 4);
bitmapByteCount = (bitmapBytesPerRow * canvasSize.height);
//Create the color space
colorSpace = CGColorSpaceCreateDeviceRGB();
bitmapData = malloc( bitmapByteCount );
//Check the the buffer is alloc'd
if( bitmapData == NULL ){
NSLog(@"Buffer could not be alloc'd");
}
//Create the context
context = CGBitmapContextCreate(bitmapData, canvasSize.width, canvasSize.height, 8, bitmapBytesPerRow, colorSpace, kCGImageAlphaPremultipliedLast);
if( context == NULL ){
NSLog(@"Context could not be created");
}
///Create the Layer
layer = CGLayerCreateWithContext(context, canvasSize, NULL);
if( layer == NULL ){
NSLog(@"Layer could not be created");
}
///Create the layer Context
layerContext = CGLayerGetContext(layer);
if( layerContext == NULL){
NSLog(@"No Layer context");
}
//Draw the image background into the bitmap context
CGContextDrawImage(context, CGRectMake(0.0f,0.0f,480,640),backgroundImage);
//Rotate and Scale Image
CGImageRef rotatedImage =rotateAndScaleImageCreate(image,rotation,scale);
//Draw a image on the layer
CGContextDrawImage(layerContext,CGRectMake(0,0,CGImageGetWidth(rotatedImage),CGImageGetHeight(rotatedImage)),rotatedImage);
CGImageRelease(rotatedImage);
//Draw the layer in the context at the coordinate
CGContextDrawLayerAtPoint( context, CGPointMake(X-CGImageGetWidth(rotatedImage)*0.5f, Y-CGImageGetHeight(rotatedImage)*0.5f), layer);
CGLayerRelease(layer);
//Get the result image
resultImage = CGBitmapContextCreateImage(context);
CGContextRelease(context);
//Cleanup
free(bitmapData);
CGColorSpaceRelease(colorSpace);
//Create UIImage
UIImage *imageReturned = [UIImage imageWithCGImage:resultImage];
CGImageRelease(resultImage);
return imageReturned;
}
如果您同时创建大量图像,请重用相同的CGContext。另外,不要创建新的旋转图像;在现有上下文中旋转图像
基本上,你只需要创建一个CGContext一次,不管你最终用它生成了多少个图像。这将大大加快速度。不要认为使用iphone可以达到您想要达到的速度(125 FPS)。我有5秒的时间来处理它们,所以我的目标是25 FPS。