What about this kind?

[iHamex]

I have tried all your examples but none of them helps. CAPTCHA images are:

So far I did:

var cbl = new CBL({
    preprocess: function(img) {
        img.invert();
        img.removeLight(50);
        img.binarize(255);
        //img.sharpen();
        img.invert();
        img.debugImage("debugPreprocessed");

        img.binarize(200);
        img.debugImage("debugPreprocessed");

        img.blur();
        img.debugImage("debugPreprocessed");

        img.removeLight(10);
        img.binarize(50);
        img.debugImage("debugPreprocessed");

        img.binarize(220);
        img.colorRegions(50, false, 6);
    },
    character_set: "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789",
    exact_characters: 6,
    exact_characters_width: 30,
    exact_characters_play: 10,
    blob_min_pixels: 1,
    blob_max_pixels: 2200,
    pattern_width: 40,
    pattern_height: 40,
    allow_console_log: true,
    blob_console_debug: true,
    perceptive_colorspace: true,
    blob_debug: "debugSegmented"
});

current result:

Any advice?

[skotz]

You could try to play off the fact that the lines are slightly darker than the letters, but with the distortion and large character set it'll probably be difficult to get good results on this one.