ximapng.cpp

用Cximage 库显示各种格式图片小程序

/*
 * File:	ximapng.cpp
 * Purpose:	Platform Independent PNG Image Class Loader and Writer
 * 07/Aug/2001 Davide Pizzolato - www.xdp.it
 * CxImage version 6.0.0 02/Feb/2008
 */

#include "ximapng.h"

#if CXIMAGE_SUPPORT_PNG

#include "ximaiter.h"

////////////////////////////////////////////////////////////////////////////////
void CxImagePNG::ima_png_error(png_struct *png_ptr, char *message)
{
	strcpy(info.szLastError,message);
	longjmp(png_ptr->jmpbuf, 1);
}
////////////////////////////////////////////////////////////////////////////////
#if CXIMAGE_SUPPORT_DECODE
////////////////////////////////////////////////////////////////////////////////
void CxImagePNG::expand2to4bpp(BYTE* prow)
{
	BYTE *psrc,*pdst;
	BYTE pos,idx;
	for(long x=head.biWidth-1;x>=0;x--){
		psrc = prow + ((2*x)>>3);
		pdst = prow + ((4*x)>>3);
		pos = (BYTE)(2*(3-x%4));
		idx = (BYTE)((*psrc & (0x03<<pos))>>pos);
		pos = (BYTE)(4*(1-x%2));
		*pdst &= ~(0x0F<<pos);
		*pdst |= (idx & 0x0F)<<pos;
	}
}
////////////////////////////////////////////////////////////////////////////////
bool CxImagePNG::Decode(CxFile *hFile)
{
	png_struct *png_ptr;
	png_info *info_ptr;
	BYTE *row_pointers=NULL;
	CImageIterator iter(this);

  cx_try
  {
    /* Create and initialize the png_struct with the desired error handler
    * functions.  If you want to use the default stderr and longjump method,
    * you can supply NULL for the last three parameters.  We also supply the
    * the compiler header file version, so that we know if the application
    * was compiled with a compatible version of the library.  REQUIRED    */
	png_ptr = png_create_read_struct(PNG_LIBPNG_VER_STRING,(void *)NULL,NULL,NULL);
	if (png_ptr == NULL)  cx_throw("Failed to create PNG structure");

	/* Allocate/initialize the memory for image information.  REQUIRED. */
	info_ptr = png_create_info_struct(png_ptr);
	if (info_ptr == NULL) {
		png_destroy_read_struct(&png_ptr, (png_infopp)NULL, (png_infopp)NULL);
		cx_throw("Failed to initialize PNG info structure");
	}

    /* Set error handling if you are using the setjmp/longjmp method (this is
    * the normal method of doing things with libpng).  REQUIRED unless you
    * set up your own error handlers in the png_create_read_struct() earlier. */
	if (setjmp(png_ptr->jmpbuf)) {
		/* Free all of the memory associated with the png_ptr and info_ptr */
		delete [] row_pointers;
		png_destroy_read_struct(&png_ptr, &info_ptr, (png_infopp)NULL);
		cx_throw("");
	}

	// use custom I/O functions
    png_set_read_fn(png_ptr, hFile, /*(png_rw_ptr)*/user_read_data);
	png_set_error_fn(png_ptr,info.szLastError,/*(png_error_ptr)*/user_error_fn,NULL);

	/* read the file information */
	png_read_info(png_ptr, info_ptr);

	if (info.nEscape == -1){
		head.biWidth = info_ptr->width;
		head.biHeight= info_ptr->height;
		info.dwType = CXIMAGE_FORMAT_PNG;
		longjmp(png_ptr->jmpbuf, 1);
	}

	/* calculate new number of channels */
	int channels=0;
	switch(info_ptr->color_type){
	case PNG_COLOR_TYPE_GRAY:
	case PNG_COLOR_TYPE_PALETTE:
		channels = 1;
		break;
	case PNG_COLOR_TYPE_GRAY_ALPHA:
		channels = 2;
		break;
	case PNG_COLOR_TYPE_RGB:
		channels = 3;
		break;
	case PNG_COLOR_TYPE_RGB_ALPHA:
		channels = 4;
		break;
	default:
		strcpy(info.szLastError,"unknown PNG color type");
		longjmp(png_ptr->jmpbuf, 1);
	}

	//find the right pixel depth used for cximage
	int pixel_depth = info_ptr->pixel_depth;
	if (channels == 1 && pixel_depth>8) pixel_depth=8;
	if (channels == 2) pixel_depth=8;
	if (channels >= 3) pixel_depth=24;

	if (!Create(info_ptr->width, info_ptr->height, pixel_depth, CXIMAGE_FORMAT_PNG)){
		longjmp(png_ptr->jmpbuf, 1);
	}

	/* get metrics */
	switch (info_ptr->phys_unit_type)
	{
	case PNG_RESOLUTION_UNKNOWN:
		SetXDPI(info_ptr->x_pixels_per_unit);
		SetYDPI(info_ptr->y_pixels_per_unit);
		break;
	case PNG_RESOLUTION_METER:
		SetXDPI((long)floor(info_ptr->x_pixels_per_unit * 254.0 / 10000.0 + 0.5));
		SetYDPI((long)floor(info_ptr->y_pixels_per_unit * 254.0 / 10000.0 + 0.5));
		break;
	}

	if (info_ptr->num_palette>0){
		SetPalette((rgb_color*)info_ptr->palette,info_ptr->num_palette);
		SetClrImportant(info_ptr->num_palette);
	} else if (info_ptr->bit_depth ==2) { //<DP> needed for 2 bpp grayscale PNGs
		SetPaletteColor(0,0,0,0);
		SetPaletteColor(1,85,85,85);
		SetPaletteColor(2,170,170,170);
		SetPaletteColor(3,255,255,255);
	} else SetGrayPalette(); //<DP> needed for grayscale PNGs
	
	int nshift = max(0,(info_ptr->bit_depth>>3)-1)<<3;

	if (info_ptr->num_trans!=0){ //palette transparency
		if (info_ptr->num_trans==1){
			if (info_ptr->color_type == PNG_COLOR_TYPE_PALETTE){
				info.nBkgndIndex = info_ptr->trans_values.index;
			} else{
				info.nBkgndIndex = info_ptr->trans_values.gray>>nshift;
			}
		}
		if (info_ptr->num_trans>1){
			RGBQUAD* pal=GetPalette();
			if (pal){
				DWORD ip;
				for (ip=0;ip<min(head.biClrUsed,(unsigned long)info_ptr->num_trans);ip++)
					pal[ip].rgbReserved=info_ptr->trans[ip];
				for (ip=info_ptr->num_trans;ip<head.biClrUsed;ip++){
					pal[ip].rgbReserved=255;
				}
				info.bAlphaPaletteEnabled=true;
			}
		}
	}

	if (channels == 3){ //check RGB binary transparency
		png_bytep trans;
		int num_trans;
		png_color_16 *image_background;
		if (png_get_tRNS(png_ptr, info_ptr, &trans, &num_trans, &image_background)){
			info.nBkgndColor.rgbRed   = (BYTE)(info_ptr->trans_values.red>>nshift);
			info.nBkgndColor.rgbGreen = (BYTE)(info_ptr->trans_values.green>>nshift);
			info.nBkgndColor.rgbBlue  = (BYTE)(info_ptr->trans_values.blue>>nshift);
			info.nBkgndColor.rgbReserved = 0;
			info.nBkgndIndex = 0;
		}
	}

	int alpha_present = (channels - 1) % 2;
	if (alpha_present){
#if CXIMAGE_SUPPORT_ALPHA	// <vho>
		AlphaCreate();
#else
		png_set_strip_alpha(png_ptr);
#endif //CXIMAGE_SUPPORT_ALPHA
	}

	// <vho> - flip the RGB pixels to BGR (or RGBA to BGRA)
	if (info_ptr->color_type & PNG_COLOR_MASK_COLOR){
		png_set_bgr(png_ptr);
	}

	// <vho> - handle cancel
	if (info.nEscape) longjmp(png_ptr->jmpbuf, 1);

	// row_bytes is the width x number of channels x (bit-depth / 8)
	row_pointers = new BYTE[info_ptr->rowbytes + 8];

	// turn on interlace handling
	int number_passes = png_set_interlace_handling(png_ptr);

	if (number_passes>1){
		SetCodecOption(1);
	} else {
		SetCodecOption(0);
	}

	int chan_offset = info_ptr->bit_depth >> 3;
	int pixel_offset = info_ptr->pixel_depth >> 3;

	for (int pass=0; pass < number_passes; pass++) {
		iter.Upset();
		int y=0;
		do	{

			// <vho> - handle cancel
			if (info.nEscape) longjmp(png_ptr->jmpbuf, 1);

#if CXIMAGE_SUPPORT_ALPHA	// <vho>
			if (AlphaIsValid()) {

				//compute the correct position of the line
				long ax,ay;
				ay = head.biHeight-1-y;
				BYTE* prow= iter.GetRow(ay);

				//recover data from previous scan
				if (info_ptr->interlace_type && pass>0 && pass!=7){
					for(ax=0;ax<head.biWidth;ax++){
						long px = ax * pixel_offset;
						if (channels == 2){
							row_pointers[px] = prow[ax];
							row_pointers[px+chan_offset]=AlphaGet(ax,ay);
						} else {
							long qx = ax * 3;
							row_pointers[px]              =prow[qx];
							row_pointers[px+chan_offset]  =prow[qx+1];
							row_pointers[px+chan_offset*2]=prow[qx+2];
							row_pointers[px+chan_offset*3]=AlphaGet(ax,ay);
						}
					}
				}

				//read next row
				png_read_row(png_ptr, row_pointers, NULL);

				//RGBA -> RGB + A
				for(ax=0;ax<head.biWidth;ax++){
					long px = ax * pixel_offset;
					if (channels == 2){
						prow[ax] = row_pointers[px];
						AlphaSet(ax,ay,row_pointers[px+chan_offset]);
					} else {
						long qx = ax * 3;
						prow[qx]  =row_pointers[px];
						prow[qx+1]=row_pointers[px+chan_offset];
						prow[qx+2]=row_pointers[px+chan_offset*2];
						AlphaSet(ax,ay,row_pointers[px+chan_offset*3]);
					}
				}
			} else
#endif // CXIMAGE_SUPPORT_ALPHA		// vho
			{
				//recover data from previous scan
				if (info_ptr->interlace_type && pass>0){
					iter.GetRow(row_pointers, info_ptr->rowbytes);
					//re-expand buffer for images with bit depth > 8
					if (info_ptr->bit_depth > 8){
						for(long ax=(head.biWidth*channels-1);ax>=0;ax--)
							row_pointers[ax*chan_offset] = row_pointers[ax];
					}