本地缓存

保存图片到沙盒

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- (void)saveImage:(UIImage *)image InSanBoxWithIndexPath:(NSInteger)indexPath {

	NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory,NSUserDomainMask, YES);
	NSString *filePath = [[paths objectAtIndex:0] stringByAppendingPathComponent:[NSString stringWithFormat:@"pic_%ld.png", indexPath]];   // 保存文件的名称
	[UIImagePNGRepresentation(image)writeToFile:filePath atomically:YES];
}

获取沙盒中的图片

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- (UIImage *)fetchImageFromSanBoxWithIndexPath:(NSInteger)indexPath
{
	NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory,NSUserDomainMask, YES);
	NSString *filePath = [[paths objectAtIndex:0] stringByAppendingPathComponent:[NSString stringWithFormat:@"pic_%ld.png", indexPath]];   // 保存文件的名称
	UIImage *img = [UIImage imageWithContentsOfFile:filePath];
	return img;
}

删除沙盒中的图片

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- (BOOL)deleteImageAtIndexPath:(NSInteger)index;
{

	NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory,NSUserDomainMask, YES);
	NSString *filePath = [[paths objectAtIndex:0] stringByAppendingPathComponent:[NSString stringWithFormat:@"pic_%ld.png", index]];

	if([[NSFileManager defaultManager] fileExistsAtPath:filePath]) {
		return  [[NSFileManager defaultManager] removeItemAtPath:filePath error:nil];
	}

	return NO;
}

修改图片

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- (UIImage *)fixOrientation:(UIImage *)aImage {

	// No-op if the orientation is already correct
	if (aImage.imageOrientation == UIImageOrientationUp)
		return aImage;
	
	// We need to calculate the proper transformation to make the image upright.
	// We do it in 2 steps: Rotate if Left/Right/Down, and then flip if Mirrored.
	CGAffineTransform transform = CGAffineTransformIdentity;
	
	switch (aImage.imageOrientation) {
		case UIImageOrientationDown:
		case UIImageOrientationDownMirrored:
		transform = CGAffineTransformTranslate(transform, aImage.size.width, aImage.size.height);
		transform = CGAffineTransformRotate(transform, M_PI);
		break;
		
		case UIImageOrientationLeft:
		case UIImageOrientationLeftMirrored:
		transform = CGAffineTransformTranslate(transform, aImage.size.width, 0);
		transform = CGAffineTransformRotate(transform, M_PI_2);
		break;
		
		case UIImageOrientationRight:
		case UIImageOrientationRightMirrored:
		transform = CGAffineTransformTranslate(transform, 0, aImage.size.height);
		transform = CGAffineTransformRotate(transform, -M_PI_2);
		break;
		default:
		break;
	}
	
	switch (aImage.imageOrientation) {
		case UIImageOrientationUpMirrored:
		case UIImageOrientationDownMirrored:
		transform = CGAffineTransformTranslate(transform, aImage.size.width, 0);
		transform = CGAffineTransformScale(transform, -1, 1);
		break;
		
		case UIImageOrientationLeftMirrored:
		case UIImageOrientationRightMirrored:
		transform = CGAffineTransformTranslate(transform, aImage.size.height, 0);
		transform = CGAffineTransformScale(transform, -1, 1);
		break;
		default:
		break;
	}
	
	// Now we draw the underlying CGImage into a new context, applying the transform
	// calculated above.
	CGContextRef ctx = CGBitmapContextCreate(NULL, aImage.size.width, aImage.size.height,
	CGImageGetBitsPerComponent(aImage.CGImage), 0,
	CGImageGetColorSpace(aImage.CGImage),
	CGImageGetBitmapInfo(aImage.CGImage));
	CGContextConcatCTM(ctx, transform);
	switch (aImage.imageOrientation) {
		case UIImageOrientationLeft:
		case UIImageOrientationLeftMirrored:
		case UIImageOrientationRight:
		case UIImageOrientationRightMirrored:
		// Grr...
			CGContextDrawImage(ctx, CGRectMake(0,0,aImage.size.height,aImage.size.width), aImage.CGImage);
		break;
		
		default:
			CGContextDrawImage(ctx, CGRectMake(0,0,aImage.size.width,aImage.size.height), aImage.CGImage);
		break;
	}
	CGImageRef cgimg = CGBitmapContextCreateImage(ctx);
	UIImage *img = [UIImage imageWithCGImage:cgimg];
	CGContextRelease(ctx);
	CGImageRelease(cgimg);
	return img;
}