scratch-paint/src/helper/bitmap.js

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import paper from '@scratch/paper';
const line = function (point1, point2, callback) {
// Bresenham line algorithm
// Fast Math.floor
let x1 = ~~point1.x;
const x2 = ~~point2.x;
let y1 = ~~point1.y;
const y2 = ~~point2.y;
const dx = Math.abs(x2 - x1);
const dy = Math.abs(y2 - y1);
const sx = (x1 < x2) ? 1 : -1;
const sy = (y1 < y2) ? 1 : -1;
let err = dx - dy;
callback(x1, y1);
while (x1 !== x2 || y1 !== y2) {
const e2 = err * 2;
if (e2 > -dy) {
err -= dy; x1 += sx;
}
if (e2 < dx) {
err += dx; y1 += sy;
}
callback(x1, y1);
}
};
const fillEllipse = function (centerX, centerY, radiusX, radiusY, context) {
// Bresenham ellipse algorithm
centerX = ~~centerX;
centerY = ~~centerY;
radiusX = ~~radiusX;
radiusY = ~~radiusY;
const twoRadXSquared = 2 * radiusX * radiusX;
const twoRadYSquared = 2 * radiusY * radiusY;
let x = radiusX;
let y = 0;
let dx = radiusY * radiusY * (1 - (radiusX << 1));
let dy = radiusX * radiusX;
let error = 0;
let stoppingX = twoRadYSquared * radiusX;
let stoppingY = 0;
while (stoppingX >= stoppingY) {
context.fillRect(centerX - x, centerY - y, x << 1, y << 1);
y++;
stoppingY += twoRadXSquared;
error += dy;
dy += twoRadXSquared;
if ((error << 1) + dx > 0) {
x--;
stoppingX -= twoRadYSquared;
error += dx;
dx += twoRadYSquared;
}
}
x = 0;
y = radiusY;
dx = radiusY * radiusY;
dy = radiusX * radiusX * (1 - (radiusY << 1));
error = 0;
stoppingX = 0;
stoppingY = twoRadXSquared * radiusY;
while (stoppingX <= stoppingY) {
context.fillRect(centerX - x, centerY - y, x * 2, y * 2);
x++;
stoppingX += twoRadYSquared;
error += dx;
dx += twoRadYSquared;
if ((error << 1) + dy > 0) {
y--;
stoppingY -= twoRadXSquared;
error += dy;
dy += twoRadXSquared;
}
}
};
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const rowBlank_ = function (imageData, width, y) {
for (let x = 0; x < width; ++x) {
if (imageData.data[(y * width << 2) + (x << 2) + 3] !== 0) return false;
}
return true;
};
const columnBlank_ = function (imageData, width, x, top, bottom) {
for (let y = top; y < bottom; ++y) {
if (imageData.data[(y * width << 2) + (x << 2) + 3] !== 0) return false;
}
return true;
};
// Adapted from Tim Down's https://gist.github.com/timdown/021d9c8f2aabc7092df564996f5afbbf
// Trims transparent pixels from edges.
const trim = function (raster) {
const width = raster.width;
const imageData = raster.getImageData(raster.bounds);
let top = 0;
let bottom = imageData.height;
let left = 0;
let right = imageData.width;
while (top < bottom && rowBlank_(imageData, width, top)) ++top;
while (bottom - 1 > top && rowBlank_(imageData, width, bottom - 1)) --bottom;
while (left < right && columnBlank_(imageData, width, left, top, bottom)) ++left;
while (right - 1 > left && columnBlank_(imageData, width, right - 1, top, bottom)) --right;
return raster.getSubRaster(new paper.Rectangle(left, top, right - left, bottom - top));
};
export {
fillEllipse,
line,
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trim
};