I have a tileset that uses 32x32 tiles:
I paint it on a canvas to purport a 32x32 tile map. However, it seems that the mathematics isn't right. Why does the canvas paint the tiles that are clearly not within the 32x32 confines of a tile?
For example:
As you can see, the top left of the canvas's 32x32 grid should be ONE tile... however it's cut off:
const appDiv = document.getElementById('app');
const tileSize = 32;
const canvasSize = 480; // 32 (tiles) * 15 (columns) = 480 pixels
const tilesAcross = canvasSize / tileSize; // (Size of Canvas [480] / Tile size [32]) = 15 columns
appDiv.innerHTML = `<h2>Canvas</h2><canvas id="map" width="${canvasSize}" height="${canvasSize}">`;
function randomIntFromInterval(min, max) {
return Math.floor(Math.random() * (max - min 1) min);
}
resizeCanvas();
// Regenerate map on resize
window.onresize = resizeCanvas;
function resizeCanvas() {
const ctx = document.getElementById('map').getContext('2d');
const image = new Image();
image.src = 'https://i.postimg.cc/k4KBLBJh/terrain.png'; // Tileset
image.onload = () => {
for (let column = 0; column < tilesAcross; column ) {
for (let row = 0; row < tilesAcross; row ) {
ctx.drawImage(
image, // Image elemnt
randomIntFromInterval(0, 5) * 32, // sx - The x-axis of top left corner of the rect of the image to draw into context.
randomIntFromInterval(0, 5) * 32, // sy - The y-axis of top left corner of the rect of the image to draw into context.
32, // sWidth - The width of the rect of the image to draw into context.
32, // sHeight - The height of the rect of the image to draw into the destination context.
row * 32, // dx - The x-axis coordinate in the canvas at which to place the top-left corner of the image.
column * 32, // dy - The y-axis coordinate in the canvas at which to place the top-left corner of the image.
32, // dWidth - The width to draw the image in the canvas. This allows scaling of the drawn image.
32 // dHeight- The width to draw the image in the canvas. This allows scaling of the drawn image.
);
}
}
};
}
canvas {
background: black;
}
<div id="app"></div>
<style src="./style.css"></style>
CodePudding user response:
The tiles in your image are not 32x32px
, more like 28.56px
.
I think you need to re-render the spritesheet. You won't get happy with this one because you'll always have lines at the edges where for one row/column the pixels of two tiles have been interpolated.
And if you stretch them then they will get blurry.
const appDiv = document.getElementById('app');
const tileSize = 32;
const canvasSize = 480; // 32 (tiles) * 15 (columns) = 480 pixels
const tilesAcross = canvasSize / tileSize; // (Size of Canvas [480] / Tile size [32]) = 15 columns
appDiv.innerHTML = `<h2>Canvas</h2><canvas id="map" width="${canvasSize}" height="${canvasSize}">`;
function randomIntFromInterval(min, max) {
return Math.floor(Math.random() * (max - min 1) min);
}
resizeCanvas();
// Regenerate map on resize
window.onresize = resizeCanvas;
function resizeCanvas() {
const ctx = document.getElementById('map').getContext('2d');
const image = new Image();
image.src = 'https://i.postimg.cc/k4KBLBJh/terrain.png'; // Tileset
image.onload = () => {
const {naturalWidth, naturalHeight} = image;
const tileWidth = image.naturalWidth / 9;
const tileHeight = image.naturalHeight / 28;
console.log({
tileWidth,
tileHeight,
naturalWidth,
naturalHeight,
})
for (let column = 0; column < tilesAcross; column ) {
for (let row = 0; row < tilesAcross; row ) {
ctx.drawImage(
image, // Image elemnt
randomIntFromInterval(0, 5) * tileWidth, // sx - The x-axis of top left corner of the rect of the image to draw into context.
randomIntFromInterval(0, 5) * tileHeight, // sy - The y-axis of top left corner of the rect of the image to draw into context.
tileWidth, // sWidth - The width of the rect of the image to draw into context.
tileHeight, // sHeight - The height of the rect of the image to draw into the destination context.
row * 32, // dx - The x-axis coordinate in the canvas at which to place the top-left corner of the image.
column * 32, // dy - The y-axis coordinate in the canvas at which to place the top-left corner of the image.
32, // dWidth - The width to draw the image in the canvas. This allows scaling of the drawn image.
32 // dHeight- The width to draw the image in the canvas. This allows scaling of the drawn image.
);
}
}
};
}
canvas {
background: black;
}
<div id="app"></div>
<style src="./style.css"></style>