Spinning circle with transloadit. Is it possible with watermark or image rotation?

I'm trying to achieve a spinning circle with artwork as a mask. From what I've seen there is no way to use a moving watermark or an automatic rotation of an image. Is it possible with transloadit?

The result should be a "vinyl" spinning.

Solution

This question is quite complex to answer, but it's very much do-able with Transloadit. I'll be using python to answer it primarily for OpenCV, but of course you can use a language that you prefer - I'll try and make it as language agnostic as possible. I used 4 different templates to get the result we want, as well as some local python magic to tie everything together - here goes.

First we need to resize the image so it fits nicely onto the vinyl record.

{
  "steps": {
    ":original": {
      "robot": "/upload/handle"
    },
    "resize": {
      "use": ":original",
      "robot": "/image/resize",
      "format": "png",
      "resize_strategy": "fillcrop",
      "width": 350,
      "height": 350,
      "imagemagick_stack": "v2.0.7"
    }
  }
}

Now, we want to mask this image using OpenCV and NumPy like so:

# Mask the image
# Reads the input image
img = cv2.imread(img_path)
# Creates a mask with the same size as the image
mask = np.zeros(img.shape, dtype=np.uint8)
# Creates a white circle in the centre
mask = cv2.circle(mask, (175, 175), 175, (255, 255, 255), -1)
# Makes a small whole in the centre of the mask
mask = cv2.circle(mask, (175, 175), 20, (0, 0, 0), -1)
result = cv2.bitwise_and(img, mask)

This will take an image, and create a mask for it that should look like a donut.

Then, using a bitwise and operation between the image and the mask you end up with a cookie cutter of the original image

Yet we still need to remove the black background - which is what we use this template for:

{
  "steps": {
    ":original": {
      "robot": "/upload/handle"
    },
    "trimmed": {
      "use": ":original",
      "robot": "/image/resize",
      "alpha": "Activate",
      "type": "TrueColor",
      "transparent": "0,0,0",
      "imagemagick_stack": "v2.0.7"
    }
  }
}

This will just make all black pixels transparent.

We can now use Transloadit's watermark feature to overlay this image onto our vinyl record

{
  "steps": {
    ":original": {
      "robot": "/upload/handle"
    },
    "watermark": {
      "use": ":original",
      "robot": "/image/resize",
      "watermark_size": "33%",
      "watermark_position": "center",
      "imagemagick_stack": "v2.0.7"
    }
  }
}

Now, all that is left is to make it spin. What we can do is create say 60 frames, and have the image rotate, then using the /video/merge robot - to stitch it all together into a seamless GIF.

{
  "steps": {
    ":original": {
      "robot": "/upload/handle"
    },
    "rotate_image": {
      "use": ":original",
      "robot": "/image/resize",
      "rotation": "${file.basename}",
      "resize_strategy": "crop",
      "imagemagick_stack": "v2.0.7"
    },
    "animated": {
      "robot": "/video/merge",
      "use": {
        "steps": [
          {
            "name": "rotate_image",
            "as": "image"
          }
        ],
        "bundle_steps": true
      },
      "result": true,
      "ffmpeg_stack": "v4.3.1",
      "ffmpeg": {
        "f": "gif",
        "pix_fmt": "rgb24"
      }
    }
  }
}

Here I use the image's name to determine how many degrees to rotate it by - so when I'm uploading the files to the robot I will name the image based on its index in an array using this python code:

# Now we make a list of images that represent each frame
no_of_frames = 60
assembly = tl.new_assembly({'template_id': [SPINNING_VINYL_TEMPLATE_ID]})
directory = 'Assets/Frames/{image}'.format(image=img_name)
# Length of our animation in seconds
length = 2

for i in range(no_of_frames):
    if not os.path.exists(directory):
        os.mkdir(directory)
    # Creates an image based on the index in the animation
    # We pass this to the robot so it knows how many degrees to rotate the image by
    location = '{directory}/{index}.png'.format(directory=directory, index=round(i*360/no_of_frames))
    cv2.imwrite(location, finished_vinyl)
    assembly.add_file(open(location, 'rb'))

This is my end result