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#include <stdio.h>
#include <string.h>
#include <ctype.h>
#include <stdlib.h>

#include <fpdfview.h>

static void writedword(FILE *fp, unsigned int d)
{
	fputc(d & 0x000000ff, fp);
	fputc((d & 0x0000ff00) >> 8, fp);
	fputc((d & 0x00ff0000) >> 16, fp);
	fputc((d & 0xff000000) >> 24, fp);
}

static void writeword(FILE *fp, unsigned short d)
{
	fputc(d & 0x00ff, fp);
	fputc((d & 0xff00) >> 8, fp);
}

static void writebmp(unsigned int *rgb, int width, int height, int modulo)
{
	FILE *fp;
	int x, y;
	int bytewidth = width * 3 + width % 4;   // line width must be a multiple of 4 for BMPs
	unsigned char *linebuf, *bak_linebuf;
	unsigned int *tmprgb = rgb;

	modulo /= 4;
	
	if(!(fp = fopen("page.bmp", "wb"))) return;
	
	linebuf = malloc(bytewidth);
	
	fwrite("BM", 2, 1, fp);
	
	writedword(fp, bytewidth * height + 54); // size
	writedword(fp, 0);    // reserved
	writedword(fp, 0x36); // offset
	writedword(fp, 0x28); // sizeof(struct BITMAPINFO)
	writedword(fp, width);
	writedword(fp, height);
	writeword(fp, 1);   // biPlanes
	writeword(fp, 24);  // bits
	writedword(fp, 0);  // compression
	writedword(fp, 0);  // size in bytes, may be zero for no compression
	writedword(fp, 0);  // pixels per meter
	writedword(fp, 0);  // pixels per meter
	writedword(fp, 0);  // biClrUsed
	writedword(fp, 0);  // biClrImportant

	bak_linebuf = linebuf;

	tmprgb += height * modulo;

	// rgb data is stored in bottom-up format, pixel data is BGR
	for(y = 0; y < height; y++) {

		tmprgb -= modulo;
		linebuf = bak_linebuf;

		for(x = 0; x < width; x++) {
			*linebuf++ = (unsigned char) (tmprgb[x] & 0x0000ff);
			*linebuf++ = (unsigned char) ((tmprgb[x] & 0x00ff00) >> 8);
			*linebuf++ = (unsigned char) ((tmprgb[x] & 0xff0000) >> 16);
		}

		fwrite(bak_linebuf, bytewidth, 1, fp);	
	}

	free(bak_linebuf);	
	fclose(fp);
}
	
int main(int argc, char *argv[])
{
	FPDF_DOCUMENT doc;
	FPDF_PAGE page;
	FPDF_BITMAP bm;
	FPDF_LIBRARY_CONFIG config;		
	FS_MATRIX transform;
	FS_RECTF rc;
	float scale;
	int pwidth, pheight, bwidth, bheight;
	
	if(argc < 3) {
		printf("Wrong args\n");
		return 0;
	}
	
	memset(&config, 0, sizeof(config));
	config.version = 2;
		
	FPDF_InitLibraryWithConfig(&config);	
	
	if(!(doc = FPDF_LoadDocument((const char *) argv[1], NULL))) {
		FPDF_DestroyLibrary();
		printf("Failed to load PDF\n");		
		return 0;
	}	
	
	scale = atof(argv[2]);
	
	page = FPDF_LoadPage(doc, 0); 
	
        transform.a = scale;
        transform.b = 0;
        transform.c = 0;
        transform.d = scale;
        transform.e = 0;
        transform.f = 0;
        	
        pwidth = (int) FPDF_GetPageWidth(page);
        pheight = (int) FPDF_GetPageHeight(page);
        
        bwidth = (int) ((float) pwidth * scale);
        bheight = (int) ((float) pheight * scale);
       
	printf("USING SCALE: %f PAGE SIZE: %d %d BITMAP SIZE: %d %d\n", scale, pwidth, pheight, bwidth, bheight);

        bm = FPDFBitmap_Create(bwidth, bheight, 1);
        
        FPDFBitmap_FillRect(bm, 0, 0, bwidth, bheight, 0xffffffff);
        
        rc.left = 0;
        rc.top = 0;
        
#if 0   
	// when using this code there is whitespace when downscaling and
	// parts of the page are cut off when upscaling
        rc.right = (float) bwidth;
        rc.bottom = (float) bheight;
#else             
	// when using this code downscaling works fine but there is whitespace
	// when upscaling
        rc.right = (float) pwidth;
        rc.bottom = (float) pheight;
#endif
        
        FPDF_RenderPageBitmapWithMatrix(bm, page, &transform, &rc, 0);
        
        writebmp(FPDFBitmap_GetBuffer(bm), bwidth, bheight, FPDFBitmap_GetStride(bm));
        
        FPDFBitmap_Destroy(bm);
        
        FPDF_ClosePage(page);
	FPDF_CloseDocument(doc);
	        
	FPDF_DestroyLibrary();	    
	    
	return 0;
}