iOS---常用圖片處理技術

========== (one) UIImage 圖像 等比例縮放==================================

PicAfterZoomWidth:縮放後圖片寬 PicAfterZoomHeight:縮放後圖片高 (預定義)

#define PicAfterZoomWidth 320
#define PicAfterZoomHeight 480


+ (UIImage *)getPicZoomImage:(UIImage *)image {
    UIImage *img = image;
    int h = img.size.height;
    int w = img.size.width;
    if(h <= PicAfterZoomWidth && w <= PicAfterZoomHeight)
    {
        image = img;
    }
    else 
    {
        float b = (float)PicAfterZoomWidth/w < (float)PicAfterZoomHeight/h ? (float)PicAfterZoomWidth/w : (float)PicAfterZoomHeight/h;
        CGSize itemSize = CGSizeMake(b*w, b*h);

       UIGraphicsBeginImageContext(itemSize);
        CGRect imageRect = CGRectMake(0, 0, b*w, b*h);
        [img drawInRect:imageRect];
        img = UIGraphicsGetImageFromCurrentImageContext();
        UIGraphicsEndImageContext();
    }
    return img;
}

=============== ( two )把圖片 圓角 化==================================

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];
}