下午好，
我正在尝试创建一个可以在图像上书写的绘图应用程序。问题是，当我尝试这样做时，我对Draw功能有一些问题。
当我触摸屏幕开始绘制时，一切都很好，但是当我完成绘制时（通过触摸屏幕），图像从正常图像变为调整大小的图像。
我在画画时如何保持相同的图像比例？
以下是它发生的事情：
当我没有触摸屏幕时
http://www.idermo.es/IMG_0275.PNG
当我触摸并完成抽奖时，那就是
http://www.idermo.es/IMG_0276.PNG
这是我的完整代码：
// DrawViewController.m
#import "DrawViewController.h"
@interface DrawViewController ()
@end
@implementation DrawViewController
@synthesize mainImage;
@synthesize tempDrawImage;
- (void)viewDidLoad
{
red = 0.0/255.0;
green = 0.0/255.0;
blue = 0.0/255.0;
brush = 5.0;
opacity = 1.0;
self.mainImage.image = _image;
[super viewDidLoad];
}
- (void)viewDidUnload
{
[self setMainImage:nil];
[self setTempDrawImage:nil];
[super viewDidUnload];
// Release any retained subviews of the main view.
}
- (BOOL)shouldAutorotateToInterfaceOrientation:(UIInterfaceOrientation)interfaceOrientation
{
return (interfaceOrientation != UIInterfaceOrientationPortraitUpsideDown);
}
- (IBAction)pencilPressed:(id)sender {
red = 0.0/255.0;
green = 0.0/255.0;
blue = 0.0/255.0;
}
- (IBAction)reset:(id)sender {
self.mainImage.image = nil;
}
- (IBAction)save:(id)sender {
UIActionSheet *actionSheet = [[UIActionSheet alloc] initWithTitle:@""
delegate:self
cancelButtonTitle:nil
destructiveButtonTitle:nil
otherButtonTitles:@"Save to Camera Roll", @"Tweet it!", @"Cancel", nil];
[actionSheet showInView:self.view];
}
- (void)actionSheet:(UIActionSheet *)actionSheet clickedButtonAtIndex:(NSInteger)buttonIndex
{
if (buttonIndex == 1)
{
} else if(buttonIndex == 0) {
UIGraphicsBeginImageContextWithOptions(self.mainImage.bounds.size, NO, 0.0);
[self.mainImage.image drawInRect:CGRectMake(0, 0, self.mainImage.frame.size.width, self.mainImage.frame.size.height)];
UIImage *SaveImage = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
UIImageWriteToSavedPhotosAlbum(SaveImage, self,@selector(image:didFinishSavingWithError:contextInfo:), nil);
}
}
- (void)image:(UIImage *)image didFinishSavingWithError:(NSError *)error contextInfo:(void *)contextInfo
{
// Was there an error?
if (error != NULL)
{
UIAlertView *alert = [[UIAlertView alloc] initWithTitle:@"Error" message:@"Image could not be saved.Please try again" delegate:nil cancelButtonTitle:nil otherButtonTitles:@"Close", nil];
[alert show];
} else {
UIAlertView *alert = [[UIAlertView alloc] initWithTitle:@"Success" message:@"Image was successfully saved in photoalbum" delegate:nil cancelButtonTitle:nil otherButtonTitles:@"Close", nil];
[alert show];
}
}
- (void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event {
mouseSwiped = NO;
UITouch *touch = [touches anyObject];
lastPoint = [touch locationInView:self.view];
}
- (void)touchesMoved:(NSSet *)touches withEvent:(UIEvent *)event {
mouseSwiped = YES;
UITouch *touch = [touches anyObject];
CGPoint currentPoint = [touch locationInView:self.view];
UIGraphicsBeginImageContext(self.view.frame.size);
[self.tempDrawImage.image drawInRect:CGRectMake(0, 0, self.view.frame.size.width, self.view.frame.size.height)];
CGContextMoveToPoint(UIGraphicsGetCurrentContext(), lastPoint.x, lastPoint.y);
CGContextAddLineToPoint(UIGraphicsGetCurrentContext(), currentPoint.x, currentPoint.y);
CGContextSetLineCap(UIGraphicsGetCurrentContext(), kCGLineCapRound);
CGContextSetLineWidth(UIGraphicsGetCurrentContext(), brush );
CGContextSetRGBStrokeColor(UIGraphicsGetCurrentContext(), red, green, blue, 1.0);
CGContextSetBlendMode(UIGraphicsGetCurrentContext(),kCGBlendModeNormal);
CGContextStrokePath(UIGraphicsGetCurrentContext());
self.tempDrawImage.image = UIGraphicsGetImageFromCurrentImageContext();
[self.tempDrawImage setAlpha:opacity];
UIGraphicsEndImageContext();
lastPoint = currentPoint;
}
- (void)touchesEnded:(NSSet *)touches withEvent:(UIEvent *)event {
if(!mouseSwiped) {
UIGraphicsBeginImageContext(self.view.frame.size);
[self.tempDrawImage.image drawInRect:CGRectMake(0, 0, self.view.frame.size.width, self.view.frame.size.height)];
CGContextSetLineCap(UIGraphicsGetCurrentContext(), kCGLineCapRound);
CGContextSetLineWidth(UIGraphicsGetCurrentContext(), brush);
CGContextSetRGBStrokeColor(UIGraphicsGetCurrentContext(), red, green, blue, opacity);
CGContextMoveToPoint(UIGraphicsGetCurrentContext(), lastPoint.x, lastPoint.y);
CGContextAddLineToPoint(UIGraphicsGetCurrentContext(), lastPoint.x, lastPoint.y);
CGContextStrokePath(UIGraphicsGetCurrentContext());
CGContextFlush(UIGraphicsGetCurrentContext());
self.tempDrawImage.image = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
}
UIGraphicsBeginImageContext(self.mainImage.frame.size);
[self.mainImage.image drawInRect:CGRectMake(0, 0, self.view.frame.size.width, self.view.frame.size.height) blendMode:kCGBlendModeNormal alpha:1.0];
[self.tempDrawImage.image drawInRect:CGRectMake(0, 0, self.view.frame.size.width, self.view.frame.size.height) blendMode:kCGBlendModeNormal alpha:opacity];
self.mainImage.image = UIGraphicsGetImageFromCurrentImageContext();
self.tempDrawImage.image = nil;
UIGraphicsEndImageContext();
}
@end
我在画画时如何保持相同的图像比例？
提前致谢。
答案 0 :(得分：0)
我认为问题出在你的触摸结束代码的最后一部分。我认为你的UIImage（mainImage.image）小于UIImageView（mainImage）
尝试以下代码：
UIGraphicsBeginImageContext(self.mainImage.frame.size);
[self.mainImage.image drawInRect:CGRectMake((self.mainImage.frame.size.width - self.mainImage.image.size.width) / 2, (self.mainImage.frame.size.height - self.mainImage.image.size.height) / 2, self.mainImage.image.size.width, mainImage.image.size.height) blendMode:kCGBlendModeNormal alpha:1.0];//mainImage.image is smaller than mainImage's frame. So draw it at appropiate position and size, so no scaling is caused.
[self.tempDrawImage.image drawInRect:CGRectMake(0, 0, self.view.frame.size.width, self.view.frame.size.height) blendMode:kCGBlendModeNormal alpha:opacity];
self.mainImage.image = UIGraphicsGetImageFromCurrentImageContext();
self.tempDrawImage.image = nil;
UIGraphicsEndImageContext();