Sample

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+ (UIImage*)greenBubble
{
    if (sGreenBubble == nil) {
        UIImage *i = [UIImage imageNamed:@"Balloon_1.png"];
        sGreenBubble = [[i stretchableImageWithLeftCapWidth:15 topCapHeight:13] retain];
    }
    return sGreenBubble;
}

+ (UIImage*)grayBubble
{
    if (sGrayBubble == nil) {
        UIImage *i = [UIImage imageNamed:@"Balloon_2.png"];
        sGrayBubble = [[i stretchableImageWithLeftCapWidth:21 topCapHeight:13] retain];
    }
    return sGrayBubble;
}

Results:


or

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