fysxasteroids/engine/Sprite.cc

#include "Engine.h"
#include "Sprite.h"

#include <GL/gl.h>
#include <GL/glu.h>
#include <png.h>

#include <cmath>

namespace Engine {

/* 
 * Code is taken from http://en.wikibooks.org/wiki/OpenGL_Programming/Intermediate/Textures on
 * Sunday, March 14 2010.
 */
bool Sprite::LoadFromPNG (const char *filename) {
	LogDebug ("Loading png from %s", filename);

	//header for testing if it is a png
	png_byte header[8];

	//open file as binary
	FILE *fp = fopen(filename, "rb");
	if (!fp) {
		LogError ("Could not open file: %s", filename);
		return false;
	}

	//read the header
	fread(header, 1, 8, fp);

	//test if png
	int is_png = !png_sig_cmp(header, 0, 8);
	if (!is_png) {
		LogError ("Error opening png file %s: file is not a png file!", filename);
		fclose(fp);
		return false;
	}

	//create png struct
	png_structp png_ptr = png_create_read_struct(PNG_LIBPNG_VER_STRING, NULL,
			NULL, NULL);
	if (!png_ptr) {
		LogError ("Error opening png file %s: unable to read png header", filename);
		fclose(fp);
		return (false);
	}

	//create png info struct
	png_infop info_ptr = png_create_info_struct(png_ptr);
	if (!info_ptr) {
		LogError ("Error opening png file %s: unable to read png header", filename);
		png_destroy_read_struct(&png_ptr, (png_infopp) NULL, (png_infopp) NULL);
		fclose(fp);
		return (false);
	}

	//create png info struct
	png_infop end_info = png_create_info_struct(png_ptr);
	if (!end_info) {
		LogError ("Error opening png file %s: unable to read png header", filename);
		png_destroy_read_struct(&png_ptr, &info_ptr, (png_infopp) NULL);
		fclose(fp);
		return (false);
	}

	//png error stuff, not sure libpng man suggests this.
	if (setjmp(png_jmpbuf(png_ptr))) {
		LogError ("Error opening png file %s: unable to read png header", filename);
		png_destroy_read_struct(&png_ptr, &info_ptr, &end_info);
		fclose(fp);
		return (false);
	}

	//init png reading
	png_init_io(png_ptr, fp);

	//let libpng know you already read the first 8 bytes
	png_set_sig_bytes(png_ptr, 8);

	// read all the info up to the image data
	png_read_info(png_ptr, info_ptr);

	//variables to pass to get info
	int bit_depth, color_type;
	png_uint_32 tmWidth, tmHeight;

	// get info about png
	png_get_IHDR(png_ptr, info_ptr, &tmWidth, &tmHeight, &bit_depth, &color_type,
			NULL, NULL, NULL);

	//update mWidth and mHeight based on png info
	mWidth = tmWidth;
	mHeight = tmHeight;
	
	// Update the png info struct.
	png_read_update_info(png_ptr, info_ptr);

	// Row size in bytes.
	int rowbytes = png_get_rowbytes(png_ptr, info_ptr);

	// Allocate the image_data as a big block, to be given to opengl
	png_byte *image_data = new png_byte[rowbytes * mHeight];
	if (!image_data) {
		//clean up memory and close stuff
		png_destroy_read_struct(&png_ptr, &info_ptr, &end_info);
		fclose(fp);
		return false;
	}

	//row_pointers is for pointing to image_data for reading the png with libpng
	png_bytep *row_pointers = new png_bytep[mHeight];
	if (!row_pointers) {
		//clean up memory and close stuff
		png_destroy_read_struct(&png_ptr, &info_ptr, &end_info);
		delete[] image_data;
		fclose(fp);
		return false;
	}
	// set the individual row_pointers to point at the correct offsets of image_data
	for (unsigned int i = 0; i < mHeight; ++i)
		row_pointers[mHeight - 1 - i] = image_data + i * rowbytes;

	//read the png into image_data through row_pointers
	png_read_image(png_ptr, row_pointers);

	//Now generate the OpenGL texture object
	glGenTextures(1, &mGlTextureName);
	glBindTexture(GL_TEXTURE_2D, mGlTextureName);
	glTexImage2D(GL_TEXTURE_2D,0, GL_RGBA, mWidth, mHeight, 0,
			GL_RGBA, GL_UNSIGNED_BYTE, (GLvoid*) image_data);
	glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST);

	//clean up memory and close stuff
	png_destroy_read_struct(&png_ptr, &info_ptr, &end_info);
	delete[] row_pointers;
	delete[] image_data;

	fclose(fp);

	return true;
}

void Sprite::DrawAt (float xpos, float ypos, float zpos) {
	float u_start = 0., u_end = 1.;
	if (mAnimation) {
		int frame_index = floor ( (mAnimationFrameRate) * mAnimationTimer);
		u_start = static_cast<float>(frame_index) / mAnimationFrameCount;
		u_end = (frame_index + 1.) / mAnimationFrameCount;
	}

	glPushMatrix();
	glTranslatef (xpos -mScale * mWidth * 0.5, ypos, zpos -mScale * mHeight * 0.5);
	glScalef (mScale, mScale, mScale);
	glDisable(GL_DEPTH_TEST);
	glEnable(GL_TEXTURE_2D);
	glEnable(GL_BLEND);
	glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA);

	glBindTexture (GL_TEXTURE_2D, mGlTextureName);

	glBegin(GL_QUADS);
	glTexCoord2f (u_start, 0.); glVertex3f (0., 0., 0.);
	glTexCoord2f (u_end, 0.); glVertex3f (0., 0., mHeight);
	glTexCoord2f (u_end, 1.); glVertex3f (mWidth, 0., mHeight);
	glTexCoord2f (u_start, 1.); glVertex3f (mWidth, 0.,0.);
	glEnd();

	glPopMatrix();

	glDisable(GL_TEXTURE_2D);
	glEnable(GL_DEPTH_TEST);
}

void Sprite::DrawAt2D (float xpos, float ypos) {
	float u_start = 0., u_end = 1.;
	if (mAnimation) {
		int frame_index = floor ( (mAnimationFrameRate) * mAnimationTimer);
		u_start = static_cast<float>(frame_index) / mAnimationFrameCount;
		u_end = (frame_index + 1.) / mAnimationFrameCount;
	}

	glPushMatrix();
	glTranslatef (xpos -mScale * mWidth * 0.5, ypos, 0.);
	glScalef (mScale, mScale, mScale);
	// \TODO Make 2d drawing of sprites a bit nicer, seems a bit overkill for such a simple function
	glRotatef (-90, 0., 0., 1.);
	glDisable(GL_DEPTH_TEST);
	glEnable(GL_TEXTURE_2D);
	glEnable(GL_BLEND);
	glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA);

	glBindTexture (GL_TEXTURE_2D, mGlTextureName);

	glBegin(GL_QUADS);
	glTexCoord2f (u_start, 0.); glVertex2f (0., 0.);
	glTexCoord2f (u_end, 0.); glVertex2f (0., mHeight);
	glTexCoord2f (u_end, 1.); glVertex2f (mWidth, mHeight);
	glTexCoord2f (u_start, 1.); glVertex2f (mWidth,0.);
	glEnd();

	glPopMatrix();

	glDisable(GL_TEXTURE_2D);
	glEnable(GL_DEPTH_TEST);
}

void Sprite::DrawSubAt (unsigned int index, float xpos, float ypos, float zpos) {
	assert (index < mSubSpriteCount);

	float u_start = static_cast<float>(index) / mSubSpriteCount;
	float u_end = (index + 1.) / mSubSpriteCount;

	glPushMatrix();
	glTranslatef (xpos -mScale * mWidth * 0.5, ypos, zpos -mScale * mHeight * 0.5);
	glScalef (mScale, mScale, mScale);
	glDisable(GL_DEPTH_TEST);
	glEnable(GL_TEXTURE_2D);
	glEnable(GL_BLEND);
	glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA);

	glBindTexture (GL_TEXTURE_2D, mGlTextureName);

	glBegin(GL_QUADS);
	glTexCoord2f (u_start, 0.); glVertex3f (0., 0., 0.);
	glTexCoord2f (u_end, 0.); glVertex3f (0., 0., mHeight);
	glTexCoord2f (u_end, 1.); glVertex3f (mWidth, 0., mHeight);
	glTexCoord2f (u_start, 1.); glVertex3f (mWidth, 0.,0.);
	glEnd();

	glPopMatrix();

	glDisable(GL_TEXTURE_2D);
	glEnable(GL_DEPTH_TEST);
}

}