#!/usr/bin/env python
# coding: utf-8

# ### The `alpha` parameter in `geom_imshow()`

# In[1]:


import numpy as np
from lets_plot import *

LetsPlot.setup_html()


# In[2]:


# Load an image

from PIL import Image
import requests
from io import BytesIO

response = requests.get('https://github.com/JetBrains/lets-plot-docs/raw/master/source/examples/cookbook/images/fisher_boat.png')

image = Image.open(BytesIO(response.content))
im_arr = np.asarray(image)
im_arr.shape


# In[3]:


p = ggplot() + geom_point(x=112, y=112, color="dark-blue", size=100, shape=15) + ggsize(450, 450)
p + ggtitle("The background blue square") + ggsize(400, 300)


# #### 1. `alpha` parameter and color image

# In[4]:


pair1 = GGBunch()
pair1.add_plot(p + geom_imshow(im_arr) + ggtitle("no alpha (opaque image)"), 0, 0)
pair1.add_plot(p + geom_imshow(im_arr, alpha=0.7) + ggtitle("alpha=0.7"), 500, 0)
pair1


# #### 2. `alpha` parameter and grayscale image

# In[5]:


im_arr_gs = im_arr[:,:,0]
im_arr_gs.shape


# In[6]:


pair2 = GGBunch()
pair2.add_plot(p + geom_imshow(im_arr_gs) + ggtitle("no alpha (opaque image)"), 0, 0)
pair2.add_plot(p + geom_imshow(im_arr_gs, alpha=0.7) + ggtitle("alpha=0.7"), 500, 0)
pair2


# #### 3. `alpha` parameter and pseudo-color image

# In[7]:


pair3 = GGBunch()
pair3.add_plot(p + geom_imshow(im_arr_gs, "magma") + ggtitle("no alpha (opaque image)"), 0, 0)
pair3.add_plot(p + geom_imshow(im_arr_gs, "magma", alpha=0.7) + ggtitle("alpha=0.7"), 500, 0)
pair3


# #### 4. `alpha` parameter and grayscale image with transparent pixels (`NaN` values)

# In[8]:


im_arr_gs_nan=im_arr_gs.copy()
im_arr_gs_nan=im_arr_gs_nan.astype(np.float64)
im_arr_gs_nan[im_arr_gs_nan < 80] = np.nan


# In[9]:


pair4 = GGBunch()
pair4.add_plot(p + geom_imshow(im_arr_gs_nan, "magma", norm=False) + ggtitle("no alpha (opaque image)"), 0, 0)
pair4.add_plot(p + geom_imshow(im_arr_gs_nan, "magma", norm=False, alpha=0.7) + ggtitle("alpha=0.7"), 500, 0)
pair4