Datasets:
Tasks:
Image Classification
Modalities:
Image
Formats:
imagefolder
Languages:
English
Size:
100K<n<1M
Tags:
OCR
Handwriting
Character Recognition
Grayscale Images
ASCII Labels
Optical Character Recognition
License:
File size: 8,233 Bytes
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---
license: mit
task_categories:
- image-classification
language:
- en
tags:
- OCR
- Handwriting
- Character Recognition
- Grayscale Images
- ASCII Labels
- Optical Character Recognition
pretty_name: alphanum
size_categories:
- 100K<n<1M
---
# AlphaNum Dataset
## Abstract
The AlphaNum dataset is a collection of 108.791 grayscale images of handwritten characters and numerals as well as special character, each sized 24x24 pixels. This dataset is designed to bolster Optical Character Recognition (OCR) research and development.
For consistency, images extracted from the MNIST dataset have been color-inverted to match the grayscale aesthetics of the AlphaNum dataset.
## Data Sources
1) [Handwriting Characters Database](https://github.com/sueiras/handwritting_characters_database)
2) [MNIST](https://huggingface.co/datasets/mnist)
3) [AZ Handwritten Alphabets in CSV format](https://www.kaggle.com/datasets/sachinpatel21/az-handwritten-alphabets-in-csv-format)
In an effort to maintain uniformity, the dataset files have been resized to 24x24 pixels and recolored from white-on-black to black-on-white.
## Dataset Structure
### Instance Description
Each dataset instance contains an image of a handwritten character or numeral, paired with its corresponding ASCII label.
### Data Organization
The dataset is organized into three separate .zip files: `train.zip`, `test.zip`, and `validation.zip`. Each ASCII symbol is housed in a dedicated folder, the name of which corresponds to the ASCII value of the symbol.
- `train.zip` size: 55.9 MB
- `test.zip` size: 16 MB
- `validation.zip` size: 8.06 MB
## Dataset Utility
The AlphaNum dataset caters to a variety of use cases including text recognition, document processing, and machine learning tasks. It is particularly instrumental in the development, fine-tuning, and enhancement of OCR models.
## Null Category Image Generation
The 'null' category comprises images generated by injecting noise to mimic randomly distributed light pixels. The creation of these images is accomplished through the following Python script:
This approach is particularly valuable as it enables the model to effectively disregard specific areas of the training data by utilizing a 'null' label. By doing so, the model becomes better at recognizing letters and can ignore irrelevant parts, enhancing its performance in reallive OCR tasks.
The 'null' labelled images in this dataset have been generated using the following algorithm.
(Please note that this is a non-deterministic approach, so you will most likely get different results.)
```python
import os
import numpy as np
from PIL import Image, ImageOps, ImageEnhance
def generate_noisy_images(num_images, image_size=(24, 24) output_dir='NoisyImages', image_format='JPEG'):
if not os.path.exists(output_dir):
os.makedirs(output_dir)
for i in range(num_images):
variation_scale = abs(np.random.normal(30, 15))
# Generate random noise with reduced strength
noise = np.random.rand(image_size[0], image_size[1]) * 0.05
noise = (noise * 255).astype(np.uint8)
# Create a PIL image from the noise
image = Image.fromarray(noise, mode='L') # 'L' for grayscale
# Invert the image
inverted_image = ImageOps.invert(image)
# Enhance the contrast with increased amplitude
enhancer = ImageEnhance.Contrast(inverted_image)
contrast_enhanced_image = enhancer.enhance(variation_scale) # Increased amplitude (e.g., 3.0)
# Save the image
contrast_enhanced_image.save(os.path.join(output_dir, f'{i}.jpg'), format=image_format)
generate_noisy_images(5000)
```
example: 
## ASCII Table and Corresponding File Counts
| ASCII Value | Character | Number of Files |
|-------------|-----------|-----------------|
| 33 | ! | 207 |
| 34 | " | 267 |
| 35 | # | 152 |
| 36 | $ | 192 |
| 37 | % | 190 |
| 38 | & | 104 |
| 39 | ' | 276 |
| 40 | ( | 346 |
| 41 | ) | 359 |
| 42 | * | 128 |
| 43 | + | 146 |
| 44 | , | 320 |
| 45 | - | 447 |
| 46 | . | 486 |
| 47 | / | 259 |
| 48 | 0 | 2664 |
| 49 | 1 | 2791 |
| 50 | 2 | 2564 |
| 51 | 3 | 2671 |
| 52 | 4 | 2530 |
| 53 | 5 | 2343 |
| 54 | 6 | 2503 |
| 55 | 7 | 2679 |
| 56 | 8 | 2544 |
| 57 | 9 | 2617 |
| 58 | : | 287 |
| 59 | ; | 223 |
| 60 | < | 168 |
| 61 | = | 254 |
| 62 | > | 162 |
| 63 | ? | 194 |
| 64 | @ | 83 |
| 65 | A | 1923 |
| 66 | B | 1505 |
| 67 | C | 1644 |
| 68 | D | 1553 |
| 69 | E | 2171 |
| 70 | F | 1468 |
| 71 | G | 1443 |
| 72 | H | 1543 |
| 73 | I | 1888 |
| 74 | J | 1470 |
| 75 | K | 1504 |
| 76 | L | 1692 |
| 77 | M | 1484 |
| 78 | N | 1683 |
| 79 | O | 2097 |
| 80 | P | 1605 |
| 81 | Q | 1409 |
| 82 | R | 1811 |
| 83 | S | 1786 |
| 84 | T | 1729 |
| 85 | U | 1458 |
| 86 | V | 1405 |
| 87 | W | 1521 |
| 88 | X | 1366 |
| 89 | Y | 1456 |
| 90 | Z | 1451 |
| 91 | [ | 111 |
| 93 | ] | 104 |
| 94 | ^ | 88 |
| 95 | _ | 80 |
| 96 | ` | 42 |
| 97 | a | 2219 |
| 98 | b | 624 |
| 99 | c | 880 |
| 100 | d | 1074 |
| 101 | e | 2962 |
| 102 | f | 608 |
| 103 | g | 760 |
| 104 | h | 990 |
| 105 | i | 2035 |
| 106 | j | 427 |
| 107 | k | 557 |
| 108 | l | 1415 |
| 109 | m | 879 |
| 110 | n | 1906 |
| 111 | o | 2048 |
| 112 | p | 786 |
| 113 | q | 427 |
| 114 | r | 1708 |
| 115 | s | 1557 |
| 116 | t | 1781 |
| 117 | u | 1319 |
| 118 | v | 555 |
| 119 | w | 680 |
| 120 | x | 463 |
| 121 | y | 680 |
| 122 | z | 505 |
| 123 | { | 73 |
| 124 | \| | 91 |
| 125 | } | 77 |
| 126 | ~ | 59 |
| 999 | null | 4999 | |