Installing pngwriter: a library to write png image

To install pngwrite we need to install to helper library before we install pngwriter.
1. libpng
2. freetype2

We can use fink or macport to install them. Using macport

-> port install libpng
-> port install freetype

both will be installed on /opt/local directory.
(.h files in /opt/local/include .dylib files in /opt/local/lib)

Then we can download the pngwriter from here.
PNGWRITER

To install pngwriter
1. untar the zipped file.
The go inside the folder.
->make
->make install

This will install the pngwriter in /usr/local
(.h files in /usr/local/include and .dylib files in /usr/local/lib)

To use the pngwriter library we need just to add the pngwriter.h file.
#include (pngwriter.h)
int main()
{
pngwriter image(200, 300, 1.0, "out.png");
image.plot(30, 40, 1.0, 0.0, 0.0);
image.close();
return 0;
}
Let this be a sample program write_test.cpp.

To compile the program we need to the following command
g++ write_test.cpp -o test -I/opt/local/include/freetype2 -I/opt/local/include
-I/usr/local/include -L/usr/local/lib -L/opt/local/lib -lpng -lpngwriter -lz -lfreetype

(Note: you have to specifically give the include path for freetype -I/opt/local/include/freetype2 -I/opt/local/include.
And: since pngwriter is installed on /usr/local/include, so is the include path for pngwriter. The lib files are on -L/opt/local/lib (for freetype and libpng ) and -L/usr/local/lib ( for pngwriter ).

(Note: pngwriter assumes the lower left corner to be origin(0,0) and upper right corner is at (width, height))

Sample pngwriter code:
----------------------

This program reads two images and finds the HSV components (of the corresponding white region of the segmented binary image.) of the color image.

int main(int argc, char* argv[])
{
if ( argc < 4 )
{
cerr << "Usage: area " << endl;
return -1;
}
//
// MagickCore::SetMagickResourceLimit(MagickCore::MemoryResource, 1536);
// MagickCore::SetMagickResourceLimit(MagickCore::MapResource, 2048);
// Image* img = new Image(argv[1]);


map mapHSV_H;
map mapHSV_S;
map mapHSV_V;

// read the segmented image
pngwriter imageSegmented;
imageSegmented.readfromfile(argv[1]);

// read the color image

pngwriter imageColor;
imageColor.readfromfile(argv[2]);

int widthS = imageSegmented.getwidth();
int heightS = imageSegmented.getheight();

int widthC = imageColor.getwidth();
int heightC = imageColor.getheight();

int width, height;

if ( widthS == widthC && heightS == heightC) {
width = widthS, height = heightS;
} else {
cerr<<"Unequal dimension of the two input images"< exit(1);
}


for (int j=0; j for (int i=0; i
// read the segmented image if the pixel is white then find the HSV component of that pixel
double red = imageSegmented.dread(i, j, RGB_R);
double green = imageSegmented.dread(i, j, RGB_G);
double blue = imageSegmented.dread(i, j, RGB_B);

cout<<"R = "<BlogThis!