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Add Transparency to an Image - Python

This tutorial shows how to create and save a transparent area in an image applying two different techniques in a Python application using the LEADTOOLS SDK.

Overview
Summary	This tutorial covers how to add transparency to images in a Python application.
Completion Time	20 minutes
Visual Studio Project	Download tutorial project (1 KB)
Platform	Python Console Application
IDE	Visual Studio 2022
Runtime Target	Python 3.10 or Higher
Development License	Download LEADTOOLS
Try it in another language	C#: .NET 6+ (Console) C API: C DLL (Windows) Python: Python

Required Knowledge

Get familiar with the basic steps of creating a project by reviewing the Add References and Set a License tutorial, before working on the Add Transparency to an Image - Python tutorial.

Create the Project and Add LEADTOOLS References

Start with a copy of the project created in the Add References and Set a License tutorial. If the project is not available, follow the steps in that tutorial to create it.

The references needed depend upon the purpose of the project.

This tutorial requires the following DLLs:

Leadtools.dll
Leadtools.Codecs.dll

For a complete list of which DLL files are required for your application, refer to Files to be Included With Your Application.

Set the License File

The License unlocks the features needed for the project. It must be set before any toolkit function is called. For details, including tutorials for different platforms, refer to Setting a Runtime License.

There are two types of runtime licenses:

Evaluation license, obtained at the time the evaluation toolkit is downloaded. It allows the toolkit to be evaluated.
Deployment license. If a Deployment license file and developer key are needed, refer to Obtaining a License.

Add the Code to Create Alpha Channel Transparency

With the project created, the references added, and the license set, coding can begin.

In the Solution Explorer, open Project-Name.pyand place the following references below the "Add references to LEADTOOLS" comment

# Add references to LEADTOOLS 
from leadtools import LibraryLoader 
LibraryLoader.add_reference("Leadtools") 
from Leadtools import * 
LibraryLoader.add_reference("Leadtools.Codecs") 
from Leadtools.Codecs import * 
from Leadtools.ImageProcessing import * 
from System.IO import *

In the Project-Name.py file add a new method called add_alpha_transparency() that takes an image and sets all white and near-white areas as transparent by manipulating the image's alpha channel.

def add_alpha_transparency(input_image): 
     
    # create an 8-bit image to use later as Alpha channel 
    alpha = input_image.CreateAlphaImage() 
 
    # Fill the alpha channel with white to cause all pixels to be opaque 
    fill = FillCommand(RasterColor.White) 
    fill.Run(alpha) 
 
    # Find white and near-white pixels in the input image and create a region from them 
    color_low = RasterColor(245, 245, 245) 
    color_hi = RasterColor.White 
    input_image.AddColorRgbRangeToRegion(color_low, color_hi, RasterRegionCombineMode.Set) 
 
    # copy the region to the alpha image 
    alpha.SetRegion(None, input_image.GetRegion(None), RasterRegionCombineMode.Set) 
    input_image.MakeRegionEmpty() 
 
    # Fill the region with black to represent transparent pixels 
    fill.Color = RasterColor.Black 
    fill.Run(alpha) 
    output_image = input_image.Clone() 
    output_image.SetAlphaImage(alpha) 
    return output_image

Add the Code to Set a Specific Color as Transparent

Add a new method called add_transparent_color() that takes an image and converts all white and near-white areas to pure white, then marks the white color as transparent.

def add_transparent_color(input_image): 
    output_image = input_image.Clone() 
 
    # Find white and near-white pixels in the input image and create a region from them 
    color_low = RasterColor(245, 245, 245) 
    color_hi = RasterColor.White 
    output_image.AddColorRgbRangeToRegion(color_low, color_hi, RasterRegionCombineMode.Set) 
 
    # Fill the region with a single white color to enable setting it as a unique transparent color 
    fill = FillCommand(RasterColor.White) 
    fill.Run(output_image) 
    output_image.Transparent = True 
    output_image.TransparentColor = RasterColor.White 
    output_image.MakeRegionEmpty() 
    return output_image

Add the Code to Load an Image and Save it With Transparency

In the main() method, load a base image to have transparency added to it and pass it to the 2 methods created above:

Pass the base image to add_alpha_transparency(), then save the resulting image as 32-bit PNG to store the transparency alpha channel with it.
Pass the base image to add_transparent_color(), then save the resulting image either as PNG or GIF, since both formats support transparent color.

# Add the below code to the `main()` method after the `Support.set_license()` method call 
codecs = RasterCodecs() 
 
image = codecs.Load(r"C:\LEADTOOLS22\Resources\Images\testframe1.jpg") 
 
# Create a new image with a transparency alpha channel from near-white parts of the image 
image_with_alpha = add_alpha_transparency(image) 
     
# Save as 32-bit PNG to store alpha channel with image 
codecs.Save(image_with_alpha, r"C:\LEADTOOLS22\Resources\Images\imagePlusAlpha.png", RasterImageFormat.Png, 32) 
 
# Create a new image with a transparency alpha channel from near-white parts of the image 
image_with_transparent_color = add_transparent_color(image) 
 
# Save as 8-bit GIF to store image with transparent color 
codecs.Save(image_with_transparent_color, r"C:\LEADTOOLS22\Resources\Images\imageWithTranspColor.gif", RasterImageFormat.Gif, 8)

Handling Streams

To load the file using MemoryStream, replace the code in the main() method with the following:

def main(): 
 
    Support.set_license(os.path.join(DemosTools.get_root(), "C:/LEADTOOLS22/Support/Common/License")) 
 
    codecs = RasterCodecs() 
 
    filepath = r"C:\LEADTOOLS22\Resources\Images\testframe1.jpg" 
    bytes = File.ReadAllBytes(filepath) 
    ms = MemoryStream(bytes) 
    image = codecs.Load(ms) 
 
    #image = codecs.Load(r"C:\LEADTOOLS22\Resources\Images\testframe1.jpg") 
 
    # Create a new image with a transparency alpha channel from near-white parts of the image 
    image_with_alpha = add_alpha_transparency(image) 
     
    # Save as 32-bit PNG to store alpha channel with image 
    codecs.Save(image_with_alpha, r"C:\LEADTOOLS22\Resources\Images\imagePlusAlpha.png", RasterImageFormat.Png, 32) 
 
    # Create a new image with a transparency alpha channel from near-white parts of the image 
    image_with_transparent_color = add_transparent_color(image) 
 
    # Save as 8-bit GIF to store image with transparent color 
    codecs.Save(image_with_transparent_color, r"C:\LEADTOOLS22\Resources\Images\imageWithTranspColor.gif", RasterImageFormat.Gif, 8)

Run the Project

Run the project by pressing F5, or by selecting Debug -> Start Debugging.

If the steps are followed correctly, the application runs and loads a JPEG image, adds transparency to it in two different ways and saves the resulting images with transparency to two different files.

Wrap-up

This tutorial showed how to add the necessary references to produce images with transparency.