Thread: Interesting problem with bmp drawing

HI!
I've been programming my bmp loader recently but got stuck in drawing this bmp... Everything is right for sqare bitmaps or bitmaps with height < width.
But when bitmap height > than it's width the function draws it in a wrong way... Here's the code:

Code:

#include "stdio.h"
#include "stdlib.h"
#include "SDL.h"
#include "bmp_load.h"

//open file
BMP::BMP(char *filename, SDL_Surface *scr)
{
        FILE *f = fopen(filename, "rb");
        if(!f)
        {
                printf("Couldn't open file %s\n", filename);
                exit(1);
        }

        fread(&bF, sizeof(BITMAPFILEHEADER), 1, f);
        fread(&bI, sizeof(BITMAPINFOHEADER), 1, f);

        if(bF.bfType != BITMAP_ID)      //it's not a bitmap file
        {
                printf("Wrong file! %s\n", filename);
                exit(1);
        }

        fseek(f, bF.bfOffBits, SEEK_SET);

        imgData = (unsigned char*)malloc(bF.bfSize);
        fread(imgData, bF.bfSize, 1, f);

        screen = scr;

        isT = 0;
        fclose(f);
}

BMP::BMP()
{

}

BMP::~BMP()
{
        delete imgData;
}

int BMP::load(char *filename, SDL_Surface *scr)
{
        FILE *f = fopen(filename, "rb");
        if(!f)
        {
                printf("Couldn't open file %s\n", filename);
                return 0;
        }

        fread(&bF, sizeof(BITMAPFILEHEADER), 1, f);
        fread(&bI, sizeof(BITMAPINFOHEADER), 1, f);

        if(bF.bfType != BITMAP_ID)      //it's not a bitmap file
        {
                printf("Wrong file! %s\n", filename);
                return 0;
        }

        fseek(f, bF.bfOffBits, SEEK_SET);

        imgData = (unsigned char*)malloc(bF.bfSize);
        fread(imgData, bF.bfSize, 1, f);

        screen = scr;

	printf("Width: %d Height: %d\n", bI.biWidth, bI.biHeight);
	
        fclose(f);
        return 1;
}

inline void BMP::draw_px(int x, int y, int r, int g, int b)
{
        color = SDL_MapRGB(screen->format, r, g, b);
        bufp = (int*)screen->pixels+y*screen->pitch/4+x;
        *bufp = color;
}

void BMP::draw(int posX, int posY)
{
        if(!isT)
        {
                posY += bI.biHeight;
                for(int j = 0; j < bI.biHeight; j++)
                        for(int i = 0; i < bI.biWidth; i++)
                                draw_px(posX+i, posY-j, imgData[j*bI.biWidth*3+i*3+2], imgData[j*bI.biWidth*3 + i*3+1], imgData[j*bI.biWidth*3 + i*3]);
        } else { 
                posY += bI.biHeight;
                for(int j = 0; j < bI.biHeight; j++)
                        for(int i = 0; i < bI.biWidth; i++)
                                if((imgData[j*bI.biWidth*3+i*3+2] != R) || (imgData[j*bI.biWidth*3+i*3+1] != G) || (imgData[j*bI.biWidth*3+i*3] != B))
                                        draw_px(posX+i, posY-j, imgData[j*bI.biWidth*3+i*3+2], imgData[j*bI.biWidth*3 + i*3+1], imgData[j*bI.biWidth*3 + i*3]);
        }


}

void BMP::setTransparent(int cR, int cG, int cB)
{
        isT = 1;
        R = cR;
        G = cG;
        B = cB;
}

In my opinion the drawing function is wrong, but it could be also the loading function...
Could you help me?

Originally Posted by Magos

Did you take into account that if the width is not a multiple of 4 there are empty bytes at the end of each scanline?

No, I didn't know it before :/
Thanks!


Hm... you're right... I don't know why I've rewritten that code twice instead of just calling load()
(these are bad sides of programming at 2 a.m. :> )