improved logo for the shell

assets/tvdos/gl.js

@@ -5,10 +5,36 @@ Has no affiliation with OpenGL by Khronos Group
  */
 
 var GL = {};
+
 GL.Tex = function(w, h, bytes) {
     this.width = w;
     this.height = h;
     this.texData = bytes;
+
+    if (!Array.isArray(bytes)) {
+        throw "Texture data is not an instance of array";
+    }
+};
+GL.SpriteSheet = function(tilew, tileh, tex) {
+    this.tileWidth = tilew;
+    this.tileHeight = tile;
+    this.texture = tex;
+
+    if (!tex instanceof GL.Tex) {
+        throw "Texture is not an instance of GL.Tex";
+    }
+
+    this.getOffX = function(x) { // THIS, or: GL.SpriteSheet.prototype.getOffX
+        var tx = tileWidth * x;
+        if (tx + tileWidth > tex.width) throw "Sprite x-offset of "+tx+" is greater than sprite width "+tex.width;
+        return tx;
+    };
+
+    this.getOffY = function(y) {
+        var ty = tileHeight * y;
+        if (ty + tileHeight > tex.height) throw "Sprite y-offset of "+ty+" is greater than sprite height "+tex.height;
+        return ty;
+    };
 };
 GL.drawTexPattern = function(tex, x, y, width, height) {
     for (var yy = 0; yy < height; yy++) {
@@ -20,6 +46,18 @@ GL.drawTexPattern = function(tex, x, y, width, height) {
         }
     }
 };
+GL.drawTexPatternOver = function(tex, x, y, width, height) {
+    for (var yy = 0; yy < height; yy++) {
+        for (var xx = 0; xx < width; xx++) {
+            var tx = xx % tex.width;
+            var ty = yy % tex.height;
+            var c = tex.texData[ty * tex.width + tx];
+            if (c != 255) {
+                graphics.plotPixel(x + xx, y + yy, c);
+            }
+        }
+    }
+};
 /*
  * Draws a texture verbatim - color of 255 will be written to the screen buffer
  */
@@ -39,4 +77,27 @@ GL.drawTexImageOver = function(tex, x, y) {
         }
     }
 };
+GL.drawSprite = function(sheet, xi, yi, x, y) {
+    var offx = sheet.getOffX(xi);
+    var offy = sheet.getOffY(yi);
+    for (var ty = 0; ty < sheet.tileHeight; ty++) {
+        for (var tx = 0; tx < sheet.tileWidth; tx++) {
+            var c = sheet.tex.texData[(ty + offy) * tex.width + (tx + offx)];
+            graphics.plotPixel(x + tx, y + ty, c);
+        }
+    }
+};
+GL.drawSpriteOver = function(sheet, xi, yi, x, y) {
+    var offx = sheet.getOffX(xi);
+    var offy = sheet.getOffY(yi);
+    for (var ty = 0; ty < sheet.tileHeight; ty++) {
+        for (var tx = 0; tx < sheet.tileWidth; tx++) {
+            var c = sheet.tex.texData[(ty + offy) * tex.width + (tx + offx)];
+            if (c != 255) {
+                graphics.plotPixel(x + tx, y + ty, c);
+            }
+        }
+    }
+};
+
 Object.freeze(GL);