画像をアスキーアートに変換（swift実装）

スズキswiftを実装したときのメモ
UIImage（width:100px程度）を入力すると、コンソールにアスキーで出力します。

https://twitter.com/shimy_net/status/473749061053333504

Objective-c

- (void)printAsciiArt:(UIImage*)image
{
    CGImageRef cgImage = [image CGImage];
    CGDataProviderRef dataProvider = CGImageGetDataProvider(cgImage);
    CFDataRef data = CGDataProviderCopyData(dataProvider);
    CFMutableDataRef mData = CFDataCreateMutableCopy(0, 0, data);
    UInt8 *pixels = (UInt8*)CFDataGetBytePtr(mData);
    
    for ( int y = 0; y < image.size.height; y = y+2 )
    {
        NSString *str = @"";
        for ( int x = 0; x < image.size.width; x++ )
        {
            UInt8 *buf = pixels + y * CGImageGetBytesPerRow(cgImage) + x * 4;
            UInt8 r = *( buf + 0 );
            UInt8 g = *( buf + 1 );
            UInt8 b = *( buf + 2 );
//            UInt8 a = *( buf + 3 );
            UInt8 l = ( r + g + b ) / 3.0;
            NSString *chr;
            if ( l <= 51 )
            {
                chr = @"@";
            }
            else if ( l > 51 && l <= 102 )
            {
                chr = @"#";
            }
            else if ( l > 102 && l <= 153 )
            {
                chr = @"=";
            }
            else if ( l > 153 && l <= 204 )
            {
                chr = @"-";
            }
            else if ( l > 204 && l <= 255 )
            {
                chr = @".";
            }
            str = [NSString stringWithFormat:@"%@%@", chr, str];
        }
        printf("%s\n", [str UTF8String]);
    }
    
    CFRelease(data);
    CFRelease(mData);
}