1.将一个指定的图形放大或缩小为指定的尺寸，可以试试以下代码
-(UIImage*)scaleToSize:(UIImage*)img size:(CGSize)size
{
// 创建一个bitmap的context
// 并把它设置成为当前正在使用的context
UIGraphicsBeginImageContext(size);
// 绘制改变大小的图片
[img drawInRect:CGRectMake(0, 0, size.width, size.height)];
// 从当前context中创建一个改变大小后的图片
UIImage* scaledImage = UIGraphicsGetImageFromCurrentImageContext();
// 使当前的context出堆栈
UIGraphicsEndImageContext();
// 返回新的改变大小后的图片
return scaledImage;
}
2.图片如何存入 iPhone 本地 Documents 的方法
在 UIButton 的 saveImage 方法里添加一张图片，以下代码可将图片存入本地的 Documents 下:
-(void)saveImage
{
NSANSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory,NSUserDomainMask, YES);
NSString *documentsDirectory = [paths objectAtIndex:0];
NSString *savedImagePath = [documentsDirectory stringByAppendingPathComponent:@"savedImage.png"];
//also be .jpg or another
UIImage *image = imageView.image; // imageView is your image
// Returns the data for the specified image in JPEG/PNG format.
NSData *imageData = UIImagePNGRepresentation(image); //UIImageJPEGRepresentation(image)
[imageData writeToFile:savedImagePath atomically:NO];
}
3. UIImageWriteToSavedPhotosAlbum保存图片的方法
用UIImageWriteToSavedPhotosAlbum往照片库里面存图片时，经常发生缩略图能看到但原图消失的问题
用 UIImageWriteToSavedPhotosAlbum(imageSave, nil, nil, nil), imageSave是UIImage类型，这样就保存进去了。
而且注意图片不宜过大，以免程序崩溃
4.保存已选取的图片，下次启动App时直接显示的方
如果您想在iPhone App里实现保存一张图片，下次再启动该App时直接自动显示该图的功能，可以使用以下方法
NSData *imageData = UIImageJPEGRepresentation(image, 1.0);
[NSData writeToFile: imagePath atomically:YES];
保存起来，启动时再读出就OK了
UIImage *_image = [[UIImage alloc]initWithContentsOfFile: imagePath];
5.在以图片为背景的view上直接写文字
-(void)drawAtPoint:(CGPoint)point withFont:(UIFont*)font orientation:(WBOrientation)orient;
-(CGPoint)drawInRect:(CGRect)rect withFont:(UIFont*)font orientation:(WBOrientation)orient alignment:(UITextAlignment)align;
UIFont * font = [UIFont fontWithName:@"Arial" size:18];
NSString *str = @"Hello World";
[str drawAtPoint:CGPointMake(0,70) withFont:font];
6.从 iPhone/iPad 图片库中读取图片的代码
如果您的App涉及到从iPhone/iPad图片库读取图片，不妨看看CocoaChina版主“angellixf”分享的代码，会为您节省很多时间。
UIImagePickerController * picker = [[UIImagePickerController alloc] init];
picker.delegate = self;
picker.sourceType = UIImagePickerControllerSourceTypePhotoLibrary;
[self presentModalViewController:picker animated:YES];
UIImagePickerControllerSourceTypePhotoLibrary,// 相片库
UIImagePickerControllerSourceTypeCamera//相机获取图片
UIImagePickerControllerSourceTypeSavedPhotosAlbum// 这个是自定义库，是由用户截图或保存到里面的
将图片保存到相片库的代码：
UIImageWriteToSavedPhotosAlbum(Image, self, @selector(image:didFinishSavingWithError:contextInfo:), nil);
图片圆角
static void addRoundedRectToPath(CGContextRef context, CGRect rect, float ovalWidth, float ovalHeight){ float fw, fh; if (ovalWidth == 0 || ovalHeight == 0) { CGContextAddRect(context, rect); return; } CGContextSaveGState(context); CGContextTranslateCTM(context, CGRectGetMinX(rect), CGRectGetMinY(rect)); CGContextScaleCTM(context, ovalWidth, ovalHeight); fw = CGRectGetWidth(rect) / ovalWidth; fh = CGRectGetHeight(rect) / ovalHeight; CGContextMoveToPoint(context, fw, fh/2); // Start at lower right corner CGContextAddArcToPoint(context, fw, fh, fw/2, fh, 1); // Top right corner CGContextAddArcToPoint(context, 0, fh, 0, fh/2, 1); // Top left corner CGContextAddArcToPoint(context, 0, 0, fw/2, 0, 1); // Lower left corner CGContextAddArcToPoint(context, fw, 0, fw, fh/2, 1); // Back to lower right CGContextClosePath(context); CGContextRestoreGState(context);}+ (id) createRoundedRectImage:(UIImage*)image size:(CGSize)size{ // the size of CGContextRef int w = size.width; int h = size.height; UIImage *img = image; CGColorSpaceRef colorSpace = CGColorSpaceCreateDeviceRGB(); CGContextRef context = CGBitmapContextCreate(NULL, w, h, 8, 4 * w, colorSpace, kCGImageAlphaPremultipliedFirst); CGRect rect = CGRectMake(0, 0, w, h); CGContextBeginPath(context); addRoundedRectToPath(context, rect, 10, 10); CGContextClosePath(context); CGContextClip(context); CGContextDrawImage(context, CGRectMake(0, 0, w, h), img.CGImage); CGImageRef imageMasked = CGBitmapContextCreateImage(context); CGContextRelease(context); CGColorSpaceRelease(colorSpace); return [UIImage imageWithCGImage:imageMasked];}直接调用createRoundedRectImage....返回圆角图片圆角大小自行修改CGContextAddArcToPoint....
转帖 : yu
