libyImage

A simple, low level, drawing library in C.

The aim of this library is to provide basic drawing feature while remaining simple and easy to use.

features

• Read PNG and PPM image files
• Save in PNG, PPM, JPEG or TIFF format
• Support transparency (alpha channel)
• Image superposition, like using calcs
• Draw lines and polygons
• Fill polygons
• Draw circles
• Draw filled circles
• Write text

dependencies

Some extern libraries are optionally used :

• libz and libpng-1.6 for png reading and writing
• libjpeg for jpeg writing
• libtiff for tiff writing

build the lib

The static library file yImage.a will be generated by make.

Various build options are available based on the formats you need to support.

default build

The default build support only PNG and need libpng and libz to be installed in your system. If the headers files of these library are not in the standard path /usr/local/include, you have to edit the Makefile and change the value of constant INCLUDEPNG to fit the correct path.

Then, simply do :

$ make

build without any dependency

You may don't need PNG support, and so want to build without libpng. In that case, the build command will be :

$ HAVE_PNG=no make

build with JPEG or TIFF support

Use

$ HAVE_JPEG=yes make

or

$ HAVE_TIFF=yes make

To add JPEG or TIFF support.

Install the library

To install libyImage in /usr/local/lib and the headers files in /usr/local/include :

$ make install

API documentation

Generate the API documentation needs doxygen (and graphviz for the graphs). Process by typing :

$ make doc

Then, open the file doc/html/index.html in a web browser.

Usage

The images are represented as simple raster in the yImage struct :

typedef struct {
    unsigned char *rgbData; /* data table : RGBRGBRGB... */
    unsigned char *alphaChanel; /* array of alpha (8bits) values */
    int rgbWidth, rgbHeight; /* image's width and height */
    int presShapeColor; /* indicate if shape_color is use or not */
    /* available if alpha_chanel == NULL and presShapeColor != 0 */
    yColor shapeColor; /* this color is for transparent pixels */
} yImage;

Short examples

Image format conversion

Here is a program png2ppm.c to convert a PNG file to the PPM binary format :

#include "yImage.h"
#include "yImage_io.h"


int main(int argc, char**argv) {

    yImage *im;

    if(argc < 2) {
        return 1;
    }

    im = y_load_png(argv[1]);

    if(im == NULL) {
        return 2;
    }

    y_save_ppm(im, "out.ppm");
    y_destroy_image(im);

    return 0;
}

Compile this program with command :

$ gcc -o png2ppm png2ppm.c -lyImage -lpng -lz -ljpeg -ltiff

Writing text

The programme hello.c create an image with text "Hello World!".

#include "yImage.h"
#include "yColor.h"
#include "yText.h"
#include "yImage_io.h"
#include <stdlib.h>

#define WIDTH 300
#define HEIGHT 50

int main(int argc, char **argv) {

    int err;
    yImage *image;
    yColor *back;

    back = y_color(WHITE);
    image = y_create_uniform_image(&err, back, WIDTH, HEIGHT);
    free(back);

    if(err) {
        fprintf(stderr, "Error %d creating image\n", err);
        return err;
    }

    y_display_text(image, 100, 17, "Hello World!");

    y_save_png(image, "hello.png");
    y_destroy_image(image);

    return 0;
}

Compile this program with command :

$ gcc -o hello hello.c -lyImage -lpng -lz -ljpeg -ltiff

Drawing exemple

This program, named fillPol, draw a yellow square centered on a red window.

#include "yImage.h"
#include "yImage_io.h"
#include "yColor.h"
#include "yDraw.h"
#include <stdlib.h>

#define WIDTH 300
#define HEIGHT 300

int main(int argc, char **argv) {

    int err;
    yImage *image;
    yColor *back, *fore;
    yPoint polygon[4];


    back = y_color(RED);
    image = y_create_uniform_image(&err, back, WIDTH, HEIGHT);
    free(back);

    if(err) {
        fprintf(stderr, "Error %d creating image\n", err);
        return err;
    }

    // Define polygon
    polygon[0].X = 50;
    polygon[0].Y = 50;
    polygon[1].X = 250;
    polygon[1].Y = 50;
    polygon[2].X = 250;
    polygon[2].Y = 250;
    polygon[3].X = 50;
    polygon[3].Y = 250;

    fore = y_color(YELLOW);
    y_fill_polygon(image,*fore,polygon,4);
    free(fore);

    y_save_png(image, "fillPol.png");
    y_destroy_image(image);

    return 0;
}

Compile this program with command :

$ gcc -o fillPol fillPol.c -DHAVE_LIBPNG -lyImage -lpng -lz