使用 drawImage 从 Tile Sheet、Sprite Sheet 或 Texture Atlas 绘制多个图像时如何防止纹理渗色？
How Can I Prevent Texture Bleeding When Using drawImage To Draw Multiple Images From A Tile Sheet, Sprite Sheet, Or Texture Atlas?
我正在使用 HTML5 canvas API 为像素艺术游戏绘制瓦片地图。渲染的瓦片地图由许多较小的图像组成，这些图像是从称为瓦片 sheet 的单个源图像中切出的。我正在使用 drawImage(src_img, sx, sy, sw, sh, dx, dy, dw, dh) 从源图像中剪切出单个图块并将它们绘制到目标 canvas 上。我正在使用 setTransform(sx, 0, 0, sy, tx, ty) 将缩放和平移应用到最终渲染图像。
我需要解决的颜色 "bleeding" 问题是由采样器引起的，采样器在缩放操作期间使用插值来混合颜色，以使事物看起来不像素化。这非常适合缩放数码照片，但不适用于像素艺术。虽然这不会对图块的中心造成太大的视觉损害，但采样器会沿着源图像中相邻图块的边缘混合颜色，这会在渲染的图块地图中产生意想不到的颜色。采样器不是仅使用落在传递给 drawImage 的源矩形内的颜色，而是混合其边界外的颜色，从而导致瓷砖之间出现间隙。
下面是我的图块 sheet 的源图像。它的实际大小是 24x24 像素，但我在 GIMP 中将它放大到 96x96 像素以便您可以看到它。我在 GIMP 的缩放工具上使用了 "Interpolation: None" 设置。如您所见，各个图块周围没有间隙或模糊的边界，因为采样器没有对颜色进行插值。 canvas API 的采样器显然会插入颜色，即使 imageSmoothingEnabled 设置为 false。
下面是 imageSmoothingEnabled 设置为 true 的渲染图块地图的一部分。左箭头指向一些红色渗入灰色瓷砖的底部。这是因为在图块 sheet 中，红色图块位于灰色图块的正下方。采样器正在将红色混合到灰色图块的底部边缘。
右边的箭头指向绿色方块的右边缘。如您所见，没有颜色渗入其中。这是因为源图像中绿色图块右侧没有任何内容，因此采样器无需混合任何内容。
下面是 imageSmoothingEnabled 设置为 false 的渲染图块图。根据比例和平移，纹理渗色仍然会发生。左箭头指向源图像中红色瓷砖的红色渗入。视觉伤害减少，但仍然存在。
右箭头指向最右边的绿色图块的问题，源图像中的灰色图块有一条灰色细线渗入，位于绿色图块的左侧。
上面两张图片是从Edge截屏的。 Chrome 和 Firefox 在隐藏流血方面做得更好。 Edge 似乎四面都在流血，但 Chrome 和 Firefox 似乎只在源矩形的右侧和底部流血。
如果有人知道如何解决这个问题，请告诉我。人们在很多论坛上询问这个问题并得到解决办法，例如：
- 用边框颜色填充源图块，以便采样器沿边缘混合相同的颜色。
- 将您的源图块放在单独的文件中，这样采样器就不会越过边界进行采样。
- 将所有内容绘制到未缩放的缓冲区 canvas，然后缩放缓冲区，确保采样器混合来自作为最终图像一部分的相邻图块的颜色，从而减轻视觉损坏。
- 将所有内容绘制到未缩放的 canvas，然后使用 CSS 使用
image-rendering:pixelated 缩放它，这基本上与之前的工作相同。
我想避免变通，但是如果您知道另一个，请post。我想知道是否有一种方法可以关闭采样或插值，或者是否有任何其他方法可以停止纹理渗色，这不是我列出的解决方法之一。
这里有一个 fiddle 展示了这个问题：https://jsfiddle.net/0rv1upjf/
您可以在我的 Github 页面上看到相同的示例：https://frankpoth.info/pages/javascript-projects/content/texture-bleeding/texture-bleeding.html
更新：
问题是由于在绘制像素时使用浮点数引起的。解决方案是避免使用浮点数，只使用整数。不幸的是，这意味着无法有效地使用 setTransform，因为缩放通常会导致浮动，但我仍然设法在图块渲染循环之外保留了一些数学知识。这是代码：
function drawRounded(source_image, context, scale) {
var offset_x = -OFFSET.x * scale + context.canvas.width * 0.5;
var offset_y = -OFFSET.y * scale + context.canvas.height * 0.5;
var map_height = (MAP_HEIGHT * scale)|0; // Similar to Math.trunc(MAP_HEIGHT * scale);
var map_width = (MAP_WIDTH * scale)|0;
var tile_size = TILE_SIZE * scale;
var rendered_tile_size = (tile_size + 1)|0; // Similar to Math.ceil(tile_size);
var map_index = 0; // Track the tile index in the map. This increases once per draw loop.
/* Loop through all tile positions in actual coordinate space so no additional calculations based on grid index are needed. */
for (var y = 0; y < map_height; y += tile_size) { // y first so we draw rows from top to bottom
for (var x = 0; x < map_width; x += tile_size) {
var frame = FRAMES[MAP[map_index]]; // The frame is the source location of the tile in the source_image.
// We have to keep the dx, dy truncation inside the loop to ensure the highest level of accuracy possible.
context.drawImage(source_image, frame.x, frame.y, TILE_SIZE, TILE_SIZE, (offset_x + x)|0, (offset_y + y)|0, rendered_tile_size, rendered_tile_size);
map_index ++;
}
}
}
我正在使用按位或或 |运算符进行四舍五入。按位或 returns 每个位位置中的一个 1，其中一个或两个操作数的相应位为 1。按位运算会将浮点数转换为整数。使用 0 作为右操作数将匹配左操作数中的所有位并截断小数点。缺点是它只支持 32 位，但我怀疑我的图块位置是否需要超过 32 位。
例如：
-10.5 | 0 == -10
10.1 | 0 == 10
10.5 | 0 == 10
二进制：
1010 | 0000 == 1010
这是一个舍入问题。
在 Safari 浏览器上已经 遇到了这个问题，当上下文被翻译成 n.5 时，Edge 和 IE 更糟糕，总是以这种或那种方式流血，Chrome for macOs 也会在 n.5 上流血，但只有在绘制 ![]()
时，
至少可以说，这是一个有缺陷的区域。
我没有查看规格以确切知道它们应该做什么，但有一个简单的解决方法。
自己计算坐标的变换，这样您就可以准确控制它们的圆角方式并确保清晰的像素。
// First calculate the scaled translations
const scaled_offset_left = -OFFSET.x * scale + context.canvas.width * 0.5;
const scaled_offset_top = -OFFSET.y * scale + context.canvas.height * 0.5;
// when drawing each tile
const dest_x = Math.floor( scaled_offset_left + (x * scale) );
const dest_y = Math.floor( scaled_offset_top + (y * scale) );
const dest_size = Math.ceil( TILE_SIZE * scale );
context.drawImage( source_image,
frame.x, frame.y, TILE_SIZE, TILE_SIZE,
dest_x, dest_y, dest_size, dest_size,
);
/* This is the tile map. Each value is a frame index in the FRAMES array. Each frame tells drawImage where to blit the source from */
const MAP = [
0, 0, 0, 1, 1, 1, 1, 2, 2, 2,
0, 1, 0, 1, 2, 2, 1, 2, 3, 2,
0, 0, 0, 1, 1, 1, 1, 2, 2, 2,
3, 3, 3, 4, 4, 4, 4, 5, 5, 5,
3, 4, 3, 4, 5, 5, 4, 5, 6, 5,
3, 4, 3, 4, 5, 5, 4, 5, 6, 5,
3, 3, 3, 4, 4, 4, 4, 5, 5, 5,
6, 6, 6, 7, 7, 7, 7, 8, 8, 8,
6, 7, 6, 7, 8, 8, 7, 8, 0, 8,
6, 6, 6, 7, 7, 7, 7, 8, 8, 8
];
const TILE_SIZE = 8; // Each tile is 8x8 pixels
const MAP_HEIGHT = 80; // The map is 80 pixels tall by 80 pixels wide
const MAP_WIDTH = 80;
/* Each frame represents the source x, y coordinates of a tile in the source image. They are indexed according to the map values */
const FRAMES = [
{ x:0, y:0 }, // map value = 0
{ x:8, y:0 }, // map value = 1
{ x:16, y:0 }, // map value = 2
{ x:0, y:8 }, // etc.
{ x:8, y:8 },
{ x:16, y:8},
{ x:0, y:16},
{ x:8, y:16},
{ x:16, y:16}
];
/* These represent the state of the keyboard keys being used. false is up and true is down */
const KEYS = {
down: false,
left: false,
right: false,
scale_down: false, // the D key
scale_up: false, // the F key
up: false
}
/* This is the scroll offset. You can also think of it as the position of the red dot in the map. */
const OFFSET = {
x: MAP_WIDTH * 0.5,
y: MAP_HEIGHT * 0.5
}; // It starts out centered in the map.
const MAX_SCALE = 75; // Max scale is 75 times larger than the actual image size.
const MIN_SCALE = 0; // Texture bleeding seems to only occur on upscale, but min scale is 0 in case you want to try it.
var scale = 4.71; // some arbitrary number that will hopefully cause the issue in your browser
/* Get the canvas drawing context. */
var context = document.querySelector('canvas').getContext('2d', {
alpha: false,
desynchronized: true
});
/* The toggle button is the div */
var toggle = document.querySelector('div');
/* The source image is a 24x24 square with 9 tile images of various colors in it. */
var base_64_image_source = 'data:image/png;base64,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';
var source_image = new Image(); // This will be the source image
/* The keyboard event handler */
function keyDownUp(event) {
var state = event.type == 'keydown' ? true : false;
switch (event.keyCode) {
case 37:
KEYS.left = state;
break;
case 38:
KEYS.up = state;
break;
case 39:
KEYS.right = state;
break;
case 40:
KEYS.down = state;
break;
case 68:
KEYS.scale_down = state;
break;
case 70:
KEYS.scale_up = state;
}
}
/* This is the update and rendering loop. It handles input and draws the images. */
function loop() {
window.requestAnimationFrame(loop); // Perpetuate the loop
/* Prepare to move and scale the image with the keyboard input */
if (KEYS.left) OFFSET.x -= 0.5;
if (KEYS.right) OFFSET.x += 0.5;
if (KEYS.up) OFFSET.y -= 0.5;
if (KEYS.down) OFFSET.y += 0.5;
if (KEYS.scale_down) scale -= 0.5 * scale / MAX_SCALE;
if (KEYS.scale_up) scale += 0.5 * scale / MAX_SCALE;
/* Keep the scale size within a defined range */
if (scale > MAX_SCALE) scale = MAX_SCALE;
else if (scale < MIN_SCALE) scale = MIN_SCALE;
/* Clear the canvas to gray. */
context.setTransform(1, 0, 0, 1, 0, 0); // Set the transform back to the identity matrix
context.fillStyle = "#202830"; // Set the fill color to gray
context.fillRect(0, 0, context.canvas.width, context.canvas.height); // fill the entire canvas
/* [EDIT]
Don't set the transform, we will calculate it ourselves
// context.setTransform(scale, 0, 0, scale, -OFFSET.x * scale + context.canvas.width * 0.5, -OFFSET.y * scale + context.canvas.height * 0.5);
First step is calculating the scaled translation
*/
const scaled_offset_left = -OFFSET.x * scale + context.canvas.width * 0.5;
const scaled_offset_top = -OFFSET.y * scale + context.canvas.height * 0.5;
let map_index = 0; // Track the tile index in the map. This increases once per draw loop.
/* Loop through all tile positions in actual coordinate space so no additional calculations based on grid index are needed. */
for (let y = 0; y < MAP_HEIGHT; y += TILE_SIZE) { // y first so we draw rows from top to bottom
for (let x = 0; x < MAP_WIDTH; x += TILE_SIZE) {
const frame = FRAMES[MAP[map_index]]; // The frame is the source location of the tile in the source_image.
/* [EDIT]
We transform the coordinates ourselves
We can control a uniform rounding by using floor and ceil
*/
const dest_x = Math.floor( scaled_offset_left + (x * scale) );
const dest_y = Math.floor( scaled_offset_top + (y * scale) );
const dest_size = Math.ceil(TILE_SIZE * scale);
context.drawImage( source_image,
frame.x, frame.y, TILE_SIZE, TILE_SIZE,
dest_x, dest_y, dest_size, dest_size
);
map_index++;
}
}
/* Draw the red dot in the center of the screen. */
context.fillStyle = "#ff0000";
/* [EDIT]
Do the same kind of calculations for the "dot" if you don't want antialiasing
// const dot_x = Math.floor( scaled_offset_left + ((OFFSET.x - 0.5) * scale) );
// const dot_y = Math.floor( scaled_offset_top + ((OFFSET.y - 0.5) * scale) );
// const dot_size = Math.ceil( scale );
// context.fillRect( dot_x, dot_y, dot_size, dot_size ); // center on the dot
But if you do want antialiasing for the dot, then just set the transformation for this drawing
*/
context.setTransform(scale, 0, 0, scale, scaled_offset_left, scaled_offset_top);
context.fillRect( (OFFSET.x - 0.5), (OFFSET.y - 0.5), 1, 1 ); // center on the dot
var smoothing = context.imageSmoothingEnabled; // Get the current smoothing value because we are going to ignore it briefly.
/* Draw the source image in the top left corner for reference. */
context.setTransform(4, 0, 0, 4, 0, 0); // Zoom in on it so it's visible.
context.imageSmoothingEnabled = false; // Set smoothing to false so we get a crisp source image representation (the real source image is not scaled at all).
context.drawImage( source_image, 0, 0 );
context.imageSmoothingEnabled = smoothing; // Set smoothing back the way it was according to the toggle choice.
}
/* Turn image smoothing on and off when you press the toggle. */
function toggleSmoothing(event) {
context.imageSmoothingEnabled = !context.imageSmoothingEnabled;
if (context.imageSmoothingEnabled) toggle.innerText = 'Smoothing Enabled'; // Make sure the button has appropriate text in it.
else toggle.innerText = 'Smoothing Disabled';
}
/* The main loop will start after the source image is loaded to ensure there is something to draw. */
source_image.addEventListener('load', (event) => {
window.requestAnimationFrame(loop); // Start the loop
}, { once: true });
/* Add the toggle smoothing click handler to the div. */
toggle.addEventListener('click', toggleSmoothing);
/* Add keyboard input */
window.addEventListener('keydown', keyDownUp);
window.addEventListener('keyup', keyDownUp);
/* Resize the canvas. */
context.canvas.width = 480;
context.canvas.height = 480;
toggleSmoothing(); // Set imageSmoothingEnabled
/* Load the source image from the base64 string. */
source_image.setAttribute('src', base_64_image_source);
* {
box-sizing: border-box;
margin: 0;
overflow: hidden;
padding: 0;
user-select: none;
}
body,
html {
background-color: #202830;
color: #ffffff;
height: 100%;
width: 100%;
}
body {
align-items: center;
display: grid;
justify-items: center;
}
p {
max-width: 640px;
}
div {
border: #ffffff 2px solid;
bottom: 4px;
cursor: pointer;
padding: 8px;
position: fixed;
right: 4px
}
<div>Smoothing Disabled</div>
<p>Use the arrow keys to scroll and the D and F keys to scale. The source image is represented on the top left. Notice the vertical and horizontal lines that appear between tiles as you scroll and scale. They are the color of the tile's neighbor in the source
image. This may be due to color sampling that occurs during scaling. Click the toggle to set imageSmoothingEnabled on the drawing context.</p>
<canvas></canvas>
请注意，要绘制“播放器”点，您可以选择手动执行相同的计算以避免抗锯齿造成的模糊，或者如果您真的想要那种模糊，那么您可以简单地设置变换仅用于这个点。在你的位置上，我什至可能会做一些模块化的事情，比如在一定规模的回合之后，然后平滑，但我会让 reader 来实现。
我正在使用 HTML5 canvas API 为像素艺术游戏绘制瓦片地图。渲染的瓦片地图由许多较小的图像组成，这些图像是从称为瓦片 sheet 的单个源图像中切出的。我正在使用 drawImage(src_img, sx, sy, sw, sh, dx, dy, dw, dh) 从源图像中剪切出单个图块并将它们绘制到目标 canvas 上。我正在使用 setTransform(sx, 0, 0, sy, tx, ty) 将缩放和平移应用到最终渲染图像。
我需要解决的颜色 "bleeding" 问题是由采样器引起的，采样器在缩放操作期间使用插值来混合颜色，以使事物看起来不像素化。这非常适合缩放数码照片，但不适用于像素艺术。虽然这不会对图块的中心造成太大的视觉损害，但采样器会沿着源图像中相邻图块的边缘混合颜色，这会在渲染的图块地图中产生意想不到的颜色。采样器不是仅使用落在传递给 drawImage 的源矩形内的颜色，而是混合其边界外的颜色，从而导致瓷砖之间出现间隙。
下面是我的图块 sheet 的源图像。它的实际大小是 24x24 像素，但我在 GIMP 中将它放大到 96x96 像素以便您可以看到它。我在 GIMP 的缩放工具上使用了 "Interpolation: None" 设置。如您所见，各个图块周围没有间隙或模糊的边界，因为采样器没有对颜色进行插值。 canvas API 的采样器显然会插入颜色，即使 imageSmoothingEnabled 设置为 false。
下面是 imageSmoothingEnabled 设置为 true 的渲染图块地图的一部分。左箭头指向一些红色渗入灰色瓷砖的底部。这是因为在图块 sheet 中，红色图块位于灰色图块的正下方。采样器正在将红色混合到灰色图块的底部边缘。
右边的箭头指向绿色方块的右边缘。如您所见，没有颜色渗入其中。这是因为源图像中绿色图块右侧没有任何内容，因此采样器无需混合任何内容。
下面是 imageSmoothingEnabled 设置为 false 的渲染图块图。根据比例和平移，纹理渗色仍然会发生。左箭头指向源图像中红色瓷砖的红色渗入。视觉伤害减少，但仍然存在。
右箭头指向最右边的绿色图块的问题，源图像中的灰色图块有一条灰色细线渗入，位于绿色图块的左侧。
上面两张图片是从Edge截屏的。 Chrome 和 Firefox 在隐藏流血方面做得更好。 Edge 似乎四面都在流血，但 Chrome 和 Firefox 似乎只在源矩形的右侧和底部流血。
如果有人知道如何解决这个问题，请告诉我。人们在很多论坛上询问这个问题并得到解决办法，例如：
- 用边框颜色填充源图块，以便采样器沿边缘混合相同的颜色。
- 将您的源图块放在单独的文件中，这样采样器就不会越过边界进行采样。
- 将所有内容绘制到未缩放的缓冲区 canvas，然后缩放缓冲区，确保采样器混合来自作为最终图像一部分的相邻图块的颜色，从而减轻视觉损坏。
- 将所有内容绘制到未缩放的 canvas，然后使用 CSS 使用
image-rendering:pixelated缩放它，这基本上与之前的工作相同。
我想避免变通，但是如果您知道另一个，请post。我想知道是否有一种方法可以关闭采样或插值，或者是否有任何其他方法可以停止纹理渗色，这不是我列出的解决方法之一。
这里有一个 fiddle 展示了这个问题：https://jsfiddle.net/0rv1upjf/
您可以在我的 Github 页面上看到相同的示例：https://frankpoth.info/pages/javascript-projects/content/texture-bleeding/texture-bleeding.html
更新：
问题是由于在绘制像素时使用浮点数引起的。解决方案是避免使用浮点数，只使用整数。不幸的是，这意味着无法有效地使用 setTransform，因为缩放通常会导致浮动，但我仍然设法在图块渲染循环之外保留了一些数学知识。这是代码：
function drawRounded(source_image, context, scale) {
var offset_x = -OFFSET.x * scale + context.canvas.width * 0.5;
var offset_y = -OFFSET.y * scale + context.canvas.height * 0.5;
var map_height = (MAP_HEIGHT * scale)|0; // Similar to Math.trunc(MAP_HEIGHT * scale);
var map_width = (MAP_WIDTH * scale)|0;
var tile_size = TILE_SIZE * scale;
var rendered_tile_size = (tile_size + 1)|0; // Similar to Math.ceil(tile_size);
var map_index = 0; // Track the tile index in the map. This increases once per draw loop.
/* Loop through all tile positions in actual coordinate space so no additional calculations based on grid index are needed. */
for (var y = 0; y < map_height; y += tile_size) { // y first so we draw rows from top to bottom
for (var x = 0; x < map_width; x += tile_size) {
var frame = FRAMES[MAP[map_index]]; // The frame is the source location of the tile in the source_image.
// We have to keep the dx, dy truncation inside the loop to ensure the highest level of accuracy possible.
context.drawImage(source_image, frame.x, frame.y, TILE_SIZE, TILE_SIZE, (offset_x + x)|0, (offset_y + y)|0, rendered_tile_size, rendered_tile_size);
map_index ++;
}
}
}
我正在使用按位或或 |运算符进行四舍五入。按位或 returns 每个位位置中的一个 1，其中一个或两个操作数的相应位为 1。按位运算会将浮点数转换为整数。使用 0 作为右操作数将匹配左操作数中的所有位并截断小数点。缺点是它只支持 32 位，但我怀疑我的图块位置是否需要超过 32 位。
例如：
-10.5 | 0 == -10
10.1 | 0 == 10
10.5 | 0 == 10
二进制：
1010 | 0000 == 1010
这是一个舍入问题。
在 Safari 浏览器上已经 n.5 时，Edge 和 IE 更糟糕，总是以这种或那种方式流血，Chrome for macOs 也会在 n.5 上流血，但只有在绘制 时，
至少可以说，这是一个有缺陷的区域。
我没有查看规格以确切知道它们应该做什么，但有一个简单的解决方法。
自己计算坐标的变换，这样您就可以准确控制它们的圆角方式并确保清晰的像素。
// First calculate the scaled translations
const scaled_offset_left = -OFFSET.x * scale + context.canvas.width * 0.5;
const scaled_offset_top = -OFFSET.y * scale + context.canvas.height * 0.5;
// when drawing each tile
const dest_x = Math.floor( scaled_offset_left + (x * scale) );
const dest_y = Math.floor( scaled_offset_top + (y * scale) );
const dest_size = Math.ceil( TILE_SIZE * scale );
context.drawImage( source_image,
frame.x, frame.y, TILE_SIZE, TILE_SIZE,
dest_x, dest_y, dest_size, dest_size,
);
/* This is the tile map. Each value is a frame index in the FRAMES array. Each frame tells drawImage where to blit the source from */
const MAP = [
0, 0, 0, 1, 1, 1, 1, 2, 2, 2,
0, 1, 0, 1, 2, 2, 1, 2, 3, 2,
0, 0, 0, 1, 1, 1, 1, 2, 2, 2,
3, 3, 3, 4, 4, 4, 4, 5, 5, 5,
3, 4, 3, 4, 5, 5, 4, 5, 6, 5,
3, 4, 3, 4, 5, 5, 4, 5, 6, 5,
3, 3, 3, 4, 4, 4, 4, 5, 5, 5,
6, 6, 6, 7, 7, 7, 7, 8, 8, 8,
6, 7, 6, 7, 8, 8, 7, 8, 0, 8,
6, 6, 6, 7, 7, 7, 7, 8, 8, 8
];
const TILE_SIZE = 8; // Each tile is 8x8 pixels
const MAP_HEIGHT = 80; // The map is 80 pixels tall by 80 pixels wide
const MAP_WIDTH = 80;
/* Each frame represents the source x, y coordinates of a tile in the source image. They are indexed according to the map values */
const FRAMES = [
{ x:0, y:0 }, // map value = 0
{ x:8, y:0 }, // map value = 1
{ x:16, y:0 }, // map value = 2
{ x:0, y:8 }, // etc.
{ x:8, y:8 },
{ x:16, y:8},
{ x:0, y:16},
{ x:8, y:16},
{ x:16, y:16}
];
/* These represent the state of the keyboard keys being used. false is up and true is down */
const KEYS = {
down: false,
left: false,
right: false,
scale_down: false, // the D key
scale_up: false, // the F key
up: false
}
/* This is the scroll offset. You can also think of it as the position of the red dot in the map. */
const OFFSET = {
x: MAP_WIDTH * 0.5,
y: MAP_HEIGHT * 0.5
}; // It starts out centered in the map.
const MAX_SCALE = 75; // Max scale is 75 times larger than the actual image size.
const MIN_SCALE = 0; // Texture bleeding seems to only occur on upscale, but min scale is 0 in case you want to try it.
var scale = 4.71; // some arbitrary number that will hopefully cause the issue in your browser
/* Get the canvas drawing context. */
var context = document.querySelector('canvas').getContext('2d', {
alpha: false,
desynchronized: true
});
/* The toggle button is the div */
var toggle = document.querySelector('div');
/* The source image is a 24x24 square with 9 tile images of various colors in it. */
var base_64_image_source = 'data:image/png;base64,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';
var source_image = new Image(); // This will be the source image
/* The keyboard event handler */
function keyDownUp(event) {
var state = event.type == 'keydown' ? true : false;
switch (event.keyCode) {
case 37:
KEYS.left = state;
break;
case 38:
KEYS.up = state;
break;
case 39:
KEYS.right = state;
break;
case 40:
KEYS.down = state;
break;
case 68:
KEYS.scale_down = state;
break;
case 70:
KEYS.scale_up = state;
}
}
/* This is the update and rendering loop. It handles input and draws the images. */
function loop() {
window.requestAnimationFrame(loop); // Perpetuate the loop
/* Prepare to move and scale the image with the keyboard input */
if (KEYS.left) OFFSET.x -= 0.5;
if (KEYS.right) OFFSET.x += 0.5;
if (KEYS.up) OFFSET.y -= 0.5;
if (KEYS.down) OFFSET.y += 0.5;
if (KEYS.scale_down) scale -= 0.5 * scale / MAX_SCALE;
if (KEYS.scale_up) scale += 0.5 * scale / MAX_SCALE;
/* Keep the scale size within a defined range */
if (scale > MAX_SCALE) scale = MAX_SCALE;
else if (scale < MIN_SCALE) scale = MIN_SCALE;
/* Clear the canvas to gray. */
context.setTransform(1, 0, 0, 1, 0, 0); // Set the transform back to the identity matrix
context.fillStyle = "#202830"; // Set the fill color to gray
context.fillRect(0, 0, context.canvas.width, context.canvas.height); // fill the entire canvas
/* [EDIT]
Don't set the transform, we will calculate it ourselves
// context.setTransform(scale, 0, 0, scale, -OFFSET.x * scale + context.canvas.width * 0.5, -OFFSET.y * scale + context.canvas.height * 0.5);
First step is calculating the scaled translation
*/
const scaled_offset_left = -OFFSET.x * scale + context.canvas.width * 0.5;
const scaled_offset_top = -OFFSET.y * scale + context.canvas.height * 0.5;
let map_index = 0; // Track the tile index in the map. This increases once per draw loop.
/* Loop through all tile positions in actual coordinate space so no additional calculations based on grid index are needed. */
for (let y = 0; y < MAP_HEIGHT; y += TILE_SIZE) { // y first so we draw rows from top to bottom
for (let x = 0; x < MAP_WIDTH; x += TILE_SIZE) {
const frame = FRAMES[MAP[map_index]]; // The frame is the source location of the tile in the source_image.
/* [EDIT]
We transform the coordinates ourselves
We can control a uniform rounding by using floor and ceil
*/
const dest_x = Math.floor( scaled_offset_left + (x * scale) );
const dest_y = Math.floor( scaled_offset_top + (y * scale) );
const dest_size = Math.ceil(TILE_SIZE * scale);
context.drawImage( source_image,
frame.x, frame.y, TILE_SIZE, TILE_SIZE,
dest_x, dest_y, dest_size, dest_size
);
map_index++;
}
}
/* Draw the red dot in the center of the screen. */
context.fillStyle = "#ff0000";
/* [EDIT]
Do the same kind of calculations for the "dot" if you don't want antialiasing
// const dot_x = Math.floor( scaled_offset_left + ((OFFSET.x - 0.5) * scale) );
// const dot_y = Math.floor( scaled_offset_top + ((OFFSET.y - 0.5) * scale) );
// const dot_size = Math.ceil( scale );
// context.fillRect( dot_x, dot_y, dot_size, dot_size ); // center on the dot
But if you do want antialiasing for the dot, then just set the transformation for this drawing
*/
context.setTransform(scale, 0, 0, scale, scaled_offset_left, scaled_offset_top);
context.fillRect( (OFFSET.x - 0.5), (OFFSET.y - 0.5), 1, 1 ); // center on the dot
var smoothing = context.imageSmoothingEnabled; // Get the current smoothing value because we are going to ignore it briefly.
/* Draw the source image in the top left corner for reference. */
context.setTransform(4, 0, 0, 4, 0, 0); // Zoom in on it so it's visible.
context.imageSmoothingEnabled = false; // Set smoothing to false so we get a crisp source image representation (the real source image is not scaled at all).
context.drawImage( source_image, 0, 0 );
context.imageSmoothingEnabled = smoothing; // Set smoothing back the way it was according to the toggle choice.
}
/* Turn image smoothing on and off when you press the toggle. */
function toggleSmoothing(event) {
context.imageSmoothingEnabled = !context.imageSmoothingEnabled;
if (context.imageSmoothingEnabled) toggle.innerText = 'Smoothing Enabled'; // Make sure the button has appropriate text in it.
else toggle.innerText = 'Smoothing Disabled';
}
/* The main loop will start after the source image is loaded to ensure there is something to draw. */
source_image.addEventListener('load', (event) => {
window.requestAnimationFrame(loop); // Start the loop
}, { once: true });
/* Add the toggle smoothing click handler to the div. */
toggle.addEventListener('click', toggleSmoothing);
/* Add keyboard input */
window.addEventListener('keydown', keyDownUp);
window.addEventListener('keyup', keyDownUp);
/* Resize the canvas. */
context.canvas.width = 480;
context.canvas.height = 480;
toggleSmoothing(); // Set imageSmoothingEnabled
/* Load the source image from the base64 string. */
source_image.setAttribute('src', base_64_image_source);
* {
box-sizing: border-box;
margin: 0;
overflow: hidden;
padding: 0;
user-select: none;
}
body,
html {
background-color: #202830;
color: #ffffff;
height: 100%;
width: 100%;
}
body {
align-items: center;
display: grid;
justify-items: center;
}
p {
max-width: 640px;
}
div {
border: #ffffff 2px solid;
bottom: 4px;
cursor: pointer;
padding: 8px;
position: fixed;
right: 4px
}
<div>Smoothing Disabled</div>
<p>Use the arrow keys to scroll and the D and F keys to scale. The source image is represented on the top left. Notice the vertical and horizontal lines that appear between tiles as you scroll and scale. They are the color of the tile's neighbor in the source
image. This may be due to color sampling that occurs during scaling. Click the toggle to set imageSmoothingEnabled on the drawing context.</p>
<canvas></canvas>
请注意，要绘制“播放器”点，您可以选择手动执行相同的计算以避免抗锯齿造成的模糊，或者如果您真的想要那种模糊，那么您可以简单地设置变换仅用于这个点。在你的位置上，我什至可能会做一些模块化的事情，比如在一定规模的回合之后，然后平滑，但我会让 reader 来实现。