PPMIO

Lei Mao

Introduction

PPM format is an uncompressed image format. Because PPM format images are the easiest format to read and write, they have been widely used in C/C++ program unit tests to verify the algorithms used in the program are correct. To make it easier to read and manipulate PPM images in C/C++, PPMIO was implemented in the repository.

PPMIO is a simple PPM image C++ I/O library that does not rely on any non-standard external libraries. It supports reading PPM RGB images to uint8_t array, and write uint8_t array to images. Note that the PPM image layout format is HWC.

Dependencies

• CMake 3.0.0+
• Valgrind 3.13.0 (Optional)

Files

.
├── CMakeLists.txt
├── libs
│   ├── CMakeLists.txt
│   ├── ppm_io.cpp
│   └── ppm_io.h
├── LICENSE.md
├── ppm_io_demo.cpp
├── README.md
└── samples
    ├── giraffe.jpg
    ├── giraffe.ppm
    ├── giraffe_replicated.ppm
    ├── kangaroo.jpg
    ├── kangaroo.ppm
    ├── kangaroo_replicated.ppm
    └── README.md

Usages

Read PPM Image From File

The library will automatically determine if the PPM image is P3 ASCII or P6 binary. The method returns 0 if successful, 1 if not. The library only supports PPM RGB images whose pixel scale is 0 to 255.

#include "ppm_io.h"

PPM ppmIn;
int status;
std::string inFilepath = './imageIn.ppm'
status = ppmIn.read(inFilepath);

Save PPM Image to File

PPM ppmOut = ppmIn;
std::string outFilepath = './imageOut.ppm'
// Switch between P3 and P6
ppmOut.setBinary(true);
status = ppmOut.write(outFilepath);

Get Image Data

// Get image height
ppmIn.getH();
// Get image width
ppmIn.getW();
// Get image handler
uint8_t * pImage = ppm.getImageHandler();

More Advanced Usages

Please check the header file ppm_io.h.

Demo

Read and Write PPM Image

giraffe_p3.ppm and portrait_p3_comment.ppm are P3 PPM, and kangaroo_p6.ppm and water-mill_p6_comment.ppm are a P6 PPM. In addition, portrait_p3_comment.ppm and water-mill_p6_comment.ppm contain addition comments in PPM file.

PPM images were read, saved and checked equivalence of input and output to make sure the library works correctly.

$ mkdir -p build
$ cd build
$ cmake ..
$ make
$ ./ppm_io_demo ../samples/giraffe_p3.ppm ../samples/giraffe_p3_replicated.ppm 
Reading PPM images from ../samples/giraffe_p3.ppm...
Reading PPM image successful.
Testing copy constructor......
Writing PPM images to ../samples/giraffe_p3_replicated.ppm...
Writing PPM image successful.
Testing assign operator...
Writing PPM images to ../samples/giraffe_p3_replicated.ppm...
Writing PPM image successful.
PPM image in and out are the same.

$ ./ppm_io_demo ../samples/kangaroo_p6.ppm ../samples/kangaroo_p6_replicated.ppm 
Reading PPM images from ../samples/kangaroo_p6.ppm...
Reading PPM image successful.
Testing copy constructor......
Writing PPM images to ../samples/kangaroo_p6_replicated.ppm...
Writing PPM image successful.
Testing assign operator...
Writing PPM images to ../samples/kangaroo_p6_replicated.ppm...
Writing PPM image successful.
PPM image in and out are the same.


$ ./ppm_io_demo ../samples/portrait_p3_comment.ppm ../samples/portrait_p3_comment_replicated.ppm 
Reading PPM images from ../samples/portrait_p3_comment.ppm...
Reading PPM image successful.
Testing copy constructor......
Writing PPM images to ../samples/portrait_p3_comment_replicated.ppm...
Writing PPM image successful.
Testing assign operator...
Writing PPM images to ../samples/portrait_p3_comment_replicated.ppm...
Writing PPM image successful.
PPM image in and out are the same.

$ ./ppm_io_demo ../samples/water-mill_p6_comment.ppm ../samples/water-mill_p6_comment_replicated.ppm
Reading PPM images from ../samples/water-mill_p6_comment.ppm...
Reading PPM image successful.
Testing copy constructor......
Writing PPM images to ../samples/water-mill_p6_comment_replicated.ppm...
Writing PPM image successful.
Testing assign operator...
Writing PPM images to ../samples/water-mill_p6_comment_replicated.ppm...
Writing PPM image successful.
PPM image in and out are the same.

Memory Leak Test

Additionally, all the runtimes above have passed Valgrind memory leak check. For example

$ valgrind --leak-check=yes ./ppm_io_demo ../samples/water-mill_p6_comment.ppm ../samples/water-mill_p6_comment_replicated.ppm
==19759== Memcheck, a memory error detector
==19759== Copyright (C) 2002-2017, and GNU GPL'd, by Julian Seward et al.
==19759== Using Valgrind-3.13.0 and LibVEX; rerun with -h for copyright info
==19759== Command: ./ppm_io_demo ../samples/water-mill_p6_comment.ppm ../samples/water-mill_p6_comment_replicated.ppm
==19759== 
Reading PPM images from ../samples/water-mill_p6_comment.ppm...
Reading PPM image successful.
Testing copy constructor......
Writing PPM images to ../samples/water-mill_p6_comment_replicated.ppm...
Writing PPM image successful.
Testing assign operator...
Writing PPM images to ../samples/water-mill_p6_comment_replicated.ppm...
Writing PPM image successful.
PPM image in and out are the same.
==19759== 
==19759== HEAP SUMMARY:
==19759==     in use at exit: 0 bytes in 0 blocks
==19759==   total heap usage: 22 allocs, 22 frees, 2,873,844 bytes allocated
==19759== 
==19759== All heap blocks were freed -- no leaks are possible
==19759== 
==19759== For counts of detected and suppressed errors, rerun with: -v
==19759== ERROR SUMMARY: 0 errors from 0 contexts (suppressed: 0 from 0)