magnifier.c

This example shows how to use some of the new functions of this version of mgsLib. It creates images from a screen region, and show them magnified in another screen. The magnification level is controlled using the mouse wheel. From the magnified image it is posible to select a pixel and show its color in a third screen.

#include <stdio.h>
#include <stdlib.h>
#include <stdarg.h>
#include <math.h>

#include "mgsLib.h"

#define MAXW    300
#define MAXH    200
#define MAXMAG  10

// Struct to hold captured image stamp data
struct imgData {
    int x, y, mode;
};

int main()
{   
    // Variables for the screens, image, mouse and some other
    int scr, scr2, scr3, image, x, y, ix, iy, btn, whl, mag = 5, recx, recy, color = MGS_CBLACK;
    // Flag for the capture mode
    unsigned char capture = 1;
    // Texts
    char magText[20], capText[20], rgbText[20];
    
    // Create three screens: main, magnifier and color display
    if ((scr = mgsCreateScreen(800, 600, "Image to magnify", 0x80C080, "tomillo.bmp")) < 0)
        exit(EXIT_FAILURE);
    if ((scr2 = mgsCreateScreen(MAXW, MAXH, "Magnified", MGS_CBLACK, NULL)) < 0)
        exit(EXIT_FAILURE);
    if ((scr3 = mgsCreateScreen(MAXW, MAXH, "Selected color", MGS_CBLACK, NULL)) < 0)
        exit(EXIT_FAILURE);
    // Capture a first image to correctly enter the main loop
    if ((image = mgsMakeImage(scr2, 0, 0, MAXW, MAXH)) < 0)
            mgsShowError(image, "Error creating first image", MGS_EFWAIT | MGS_EFWIN);
    // Big font to write messages
    mgsSetFont(scr, 40, MGS_CRED, MGS_TRANSPARENT);
    // And smaller with background to show RGB coordinates of the color
    mgsSetFont(scr3, 25, MGS_CBLACK, MGS_CWHITE);
    
    // S to exit
    puts("Press S to exit.");
    
    while(!mgsKeyPressed('S')) {
        // Mouse data is used frequently, so get them all once per frame
        x = mgsMouseX(scr);
        y = mgsMouseY(scr);
        btn = mgsMouseButtons(scr);
        whl = mgsMouseWheel(scr, 1);
        // The advanced mouse functions are used on two windows
        mgsHandleMouse(scr);
        mgsHandleMouse(scr2);
        // In capture mode update the magnification with the wheel and capture
        // the image to be displayed on scr2
        if (capture) {
            // Apply  the magnification between 2 and the maximum
            if ((whl > 0) && (mag < MAXMAG))
                mag++;
            else if ((whl < 0) && (mag > 2))
                mag--;
            // Recalculate the size to capture accordingly. 
            // The display size is constant.
            recx = MAXW / mag;
            recy = MAXH / mag;
            if (x < recx / 2) x = recx / 2;
            else if (x > 800 - recx / 2) x = 800 - recx / 2;
            if (y < recy / 2) y = recy / 2;
            else if (y > 600 - recy / 2) y = 600 - recy / 2;
            // Images do not accumulate, so release the previous one
            mgsDeleteImage(image);
            // Erase the text, only want to capture the background
            mgsClearScreen(scr);
            // Adjust the capturing rectangle for odd recx and recy near the borders
            ix = x - recx / 2;
            iy = y - recy / 2;
            if (ix + recx > 800) ix--;
            if (iy + recy > 600) iy--;
            // And capture the image
            if ((image = mgsMakeImage(scr, ix, iy, recx, recy)) < 0)
                mgsShowError(image, "Error capturing image", MGS_EFWAIT | MGS_EFWIN);
        }
        // Erase the text if not done previosly. We delay it until the last moment,
        // but the effect is the same when erasing once before the if sentence -if calculations do
        // not take long.
        else mgsClearScreen(scr);
        // Left click to toggle capture mode
        if (mgsLeftMouseClk(scr, 0, 0, 800, 600))
            capture = 1 - capture;
        // Left click on scr2 to pick a color
        if (mgsLeftMouseClk(scr2, 0, 0, MAXW, MAXH))
            color = mgsGetColor(scr2, mgsMouseX(scr2), mgsMouseY(scr2));
        // Prepare the texts to be shown
        sprintf(magText, "Magnify x %d", mag);
        sprintf(capText, "Capture %s", capture ? "ON" : "OFF");
        sprintf(rgbText, "RGB: %02X%02X%02X", color & 0xFF, (color >> 8) & 0xFF, (color >> 16) & 0xFF);
        // And last, display the objects
        // The selected color on scr3
        mgsRectangle(scr3, 0, 0, MAXW, MAXH, color);
        // The magnified image on scr2. First draw a black rectangle
        // to avoid border artifacts due to integer operations.
        // Not the best but the simplest solution
        mgsRectangle(scr2, 0, 0, MAXW, MAXH, MGS_CBLACK);
        mgsDisplayRotatedImage(scr2, image, 0, 0, mag, mag, 0, 0);
        // Both info texts on scr
        mgsPuts(scr, 10, 5, magText);
        mgsPuts(scr, 10, 55, capText);
        // RGB text on scr3
        mgsPuts(scr3, MAXW / 2 - 70, 5, rgbText);
        
        
        // Frame synchronization and screen updating
        mgsWaitFrame();
        mgsUpdateScreen(scr);
        mgsUpdateScreen(scr2);
        mgsUpdateScreen(scr3);
        
    }
    exit(EXIT_SUCCESS);
}