22. Displaying score and using PNG images
Displaying PNG images would mean several improvements for our games: easy transparency (which can be achieved also using BMP images, but in a more complicated way, using "special colors") and smaller images.
Also JPG images can be useful for backgrounds, even though not so much for characters, as they tend to blur the edges.
Both type of images can be displayed if we make minor changes to our auxiliary SdlHardware class (which we will not see in detail):
dotImage = new Image("dot.png"); enemyImage = new Image("ghostGreen.png"); pacImage = new Image("pac01r.png"); wallImage = new Image("wall.png");
Our improved "SdlHardware" will also allow us to display text on screen, using TTF fonts, with the following format:
Font sans18 = new Font("sans.ttf", 18); ... SdlHardware.WriteHiddenText("Hit SPACE to start", 300, 500, 0xCC, 0xCC, 0xCC, sans18);
Parameters for this function are: text to write, X and Y coordinates, R-G-B components of the color, and font to use.
The complete program would be almost identical to the previous version, except for the text writing commands and the name of the images:
/* First mini-graphics-game skeleton Version L: PNG images, TTF texts */ using System; public class SdlMuncher { static int x, y; static int pacSpeed; static int amountOfEnemies; static float[] xEnemy = { 150, 400, 500, 600 }; static float[] yEnemy = { 100, 200, 300, 400 }; static float[] incrXEnemy = { 5f, 3f, 6f, 4.5f }; static int[] xDot; static int[] yDot; static bool[] visible; static int amountOfDots; static Image dotImage; static Image enemyImage; static Image pacImage; static Image wallImage; static string[] map = { "-----------------", "-.......-.......-", "-.--.--.-.--.--.-", "-...............-", "-.--.-.---.-.--.-", "-....-..-..-....-", "----.--...--.----", ".................", "----.-.-.-.-.----", "-....-.-.-.-....-", "-.--.-.---.-.--.-", "-...............-", "-.--.-.---.-.--.-", "-....-.....-....-", "-----------------" }; static int score; static Font sans18; public static void Init() { bool fullScreen = false; SdlHardware.Init(800, 600, 24, fullScreen); dotImage = new Image("dot.png"); enemyImage = new Image("ghostGreen.png"); pacImage = new Image("pac01r.png"); wallImage = new Image("wall.png"); x = 32; y = 32; pacSpeed = 4; amountOfEnemies = 4; // Data for the dots // First: count how many dots are there amountOfDots = 0; for (int row = 0; row < 15; row++) { for (int column = 0; column < 17; column++) { if (map[row][column] == '.') amountOfDots++; } } xDot = new int[amountOfDots]; yDot = new int[amountOfDots]; visible = new bool[amountOfDots]; // Now, assign their coordinates int currentDot = 0; for (int row = 0; row < 15; row++) { for (int column = 0; column < 17; column++) { if (map[row][column] == '.') { xDot[currentDot] = column * 32; yDot[currentDot] = row * 32; visible[currentDot] = true; currentDot++; } } } score = 0; // Font sans18 = new Font("Joystix.ttf", 18); } public static void Intro() { Image pac = new Image("pac01r.png"); Image ghost = new Image("ghostGreen.png"); int x = -40; do { SdlHardware.ClearScreen(); SdlHardware.WriteHiddenText("Hit SPACE to start", 300, 500, 0xCC, 0xCC, 0xCC, sans18); SdlHardware.DrawHiddenImage(ghost, x - 50, 300); SdlHardware.DrawHiddenImage(pac, x, 300); SdlHardware.ShowHiddenScreen(); x += 8; if (x > 850) x = -40; SdlHardware.Pause(20); } while (!SdlHardware.KeyPressed(SdlHardware.KEY_SPC)); } public static bool CanMoveTo(int x, int y, string[] map) { bool canMove = true; for (int row = 0; row < 15; row++) { for (int column = 0; column < 17; column++) { if (map[row][column] == '-') if ((x > column * 32 - 32) && (x < column * 32 + 32) && (y > row * 32 - 32) && (y < row * 32 + 32) ) { canMove = false; } } } return canMove; } public static void Main() { Init(); Intro(); // Game Loop bool gameFinished = false; while (!gameFinished) { // Draw SdlHardware.ClearScreen(); //Console.Write("Score: {0}",score); // Background map for (int row = 0; row < 15; row++) { for (int column = 0; column < 17; column++) { if (map[row][column] == '-') SdlHardware.DrawHiddenImage(wallImage, column * 32, row * 32); } } for (int i = 0; i < amountOfDots; i++) { if (visible[i]) SdlHardware.DrawHiddenImage(dotImage, xDot[i], yDot[i]); } SdlHardware.DrawHiddenImage(pacImage, x, y); for (int i = 0; i < amountOfEnemies; i++) SdlHardware.DrawHiddenImage(enemyImage, (int)xEnemy[i], (int)yEnemy[i]); SdlHardware.WriteHiddenText("Score: "+score, 610, 100, 0x80, 0x80, 0xFF, sans18); SdlHardware.ShowHiddenScreen(); // Read keys and calculate new position if (SdlHardware.KeyPressed(SdlHardware.KEY_RIGHT) && CanMoveTo(x + pacSpeed, y, map)) x += pacSpeed; if (SdlHardware.KeyPressed(SdlHardware.KEY_LEFT) && CanMoveTo(x - pacSpeed, y, map)) x -= pacSpeed; if (SdlHardware.KeyPressed(SdlHardware.KEY_DOWN) && CanMoveTo(x, y + pacSpeed, map)) y += pacSpeed; if (SdlHardware.KeyPressed(SdlHardware.KEY_UP) && CanMoveTo(x, y - pacSpeed, map)) y -= pacSpeed; if (SdlHardware.KeyPressed(SdlHardware.KEY_ESC)) gameFinished = true; // Move enemies and environment for (int i = 0; i < amountOfEnemies; i++) { xEnemy[i] += incrXEnemy[i]; if ((xEnemy[i] < 1) || (xEnemy[i] > 760)) incrXEnemy[i] = -incrXEnemy[i]; } // Collisions, lose energy or lives, etc for (int i = 0; i < amountOfDots; i++) if (visible[i] && (x > xDot[i] - 32) && (x < xDot[i] + 32) && (y > yDot[i] - 32) && (y < yDot[i] + 32) ) { score += 10; visible[i] = false; } // Pause till next fotogram SdlHardware.Pause(40); } } }
You can download the full new version of the project, including PNG images, all the DLL
files and the updated auxiliary "SdlHardware.cs" file, in the "Google Code"
page for this project. This version is called "SdlMuncher012.zip":
code.google.com/p/sdl-muncher/
Also, you can see there the details of the SdlHardware class: code.google.com/p/sdl-muncher/source/browse/trunk/SdlHardware.cs