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unsettledgames 2021-09-18 22:32:47 +02:00
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js/_pixelEditorUtility.js
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/***********MISCELLANEOUS UTILITY FUNCTIONS**************/
// REFACTOR: put in Canvas class / IIFE
/** Tells if a pixel is empty (has alpha = 0)
*
* @param {*} pixel
*/
function isPixelEmpty(pixel) {
// If the alpha channel is 0, the current pixel is empty
return pixel[3] == 0;
}
// REFACTOR: move to eyedropper onMouseUp event?
/** Gets the eyedropped colour (the colour of the pixel pointed by the cursor when the user is using the eyedropper).
* It takes the colour of the canvas with the biggest z-index, basically the one the user can see, since it doesn't
* make much sense to sample a colour which is hidden behind a different layer
*
* @param {*} cursorLocation The position of the cursor
*/
function getEyedropperColor(cursorLocation) {
// Making sure max will take some kind of value
let max = -1;
// Using tmpColour to sample the sprite
let tmpColour;
// Returned colour
let selectedColor;
for (let i=1; i<layers.length; i++) {
// Getting the colour of the pixel in the cursorLocation
tmpColour = layers[i].context.getImageData(Math.floor(cursorLocation[0]/zoom),Math.floor(cursorLocation[1]/zoom),1,1).data;
// If it's not empty, I check if it's on the top of the previous colour
if (layers[i].canvas.style.zIndex > max || isPixelEmpty(selectedColor) || selectedColor === undefined) {
max = layers[i].canvas.style.zIndex;
if (!isPixelEmpty(tmpColour)) {
selectedColor = tmpColour;
}
}
}
// If the final colour was empty, I return black
if (isPixelEmpty(tmpColour) && selectedColor === undefined) {
selectedColor = [0, 0, 0];
}
return selectedColor;
}
// REFACTOR: private method of custom ImageData wrapper (PixelImageData?)?
/** Nearest neighbor algorithm to scale a sprite
*
* @param {*} src The source imageData
* @param {*} dst The destination imageData
*/
function nearestNeighbor (src, dst) {
let pos = 0
// Just applying the nearest neighbor algorithm
for (let y = 0; y < dst.height; y++) {
for (let x = 0; x < dst.width; x++) {
const srcX = Math.floor(x * src.width / dst.width)
const srcY = Math.floor(y * src.height / dst.height)
let srcPos = ((srcY * src.width) + srcX) * 4
dst.data[pos++] = src.data[srcPos++] // R
dst.data[pos++] = src.data[srcPos++] // G
dst.data[pos++] = src.data[srcPos++] // B
dst.data[pos++] = src.data[srcPos++] // A
}
}
}
// REFACTOR: private method of custom ImageData wrapper (PixelImageData?)?
/** Bilinear interpolation used to scale a sprite
*
* @param {*} src The source imageData
* @param {*} dst The destination imageData
*/
function bilinearInterpolation (src, dst) {
// Applying the bilinear interpolation algorithm
function interpolate (k, kMin, kMax, vMin, vMax) {
return Math.round((k - kMin) * vMax + (kMax - k) * vMin)
}
function interpolateHorizontal (offset, x, y, xMin, xMax) {
const vMin = src.data[((y * src.width + xMin) * 4) + offset]
if (xMin === xMax) return vMin
const vMax = src.data[((y * src.width + xMax) * 4) + offset]
return interpolate(x, xMin, xMax, vMin, vMax)
}
function interpolateVertical (offset, x, xMin, xMax, y, yMin, yMax) {
const vMin = interpolateHorizontal(offset, x, yMin, xMin, xMax)
if (yMin === yMax) return vMin
const vMax = interpolateHorizontal(offset, x, yMax, xMin, xMax)
return interpolate(y, yMin, yMax, vMin, vMax)
}
let pos = 0
for (let y = 0; y < dst.height; y++) {
for (let x = 0; x < dst.width; x++) {
const srcX = x * src.width / dst.width
const srcY = y * src.height / dst.height
const xMin = Math.floor(srcX)
const yMin = Math.floor(srcY)
const xMax = Math.min(Math.ceil(srcX), src.width - 1)
const yMax = Math.min(Math.ceil(srcY), src.height - 1)
dst.data[pos++] = interpolateVertical(0, srcX, xMin, xMax, srcY, yMin, yMax) // R
dst.data[pos++] = interpolateVertical(1, srcX, xMin, xMax, srcY, yMin, yMax) // G
dst.data[pos++] = interpolateVertical(2, srcX, xMin, xMax, srcY, yMin, yMax) // B
dst.data[pos++] = interpolateVertical(3, srcX, xMin, xMax, srcY, yMin, yMax) // A
}
}
}
// REFACTOR: public static method of custom ImageData wrapper (PixelImageData?)?
/** Resizes an imageData depending on the algorithm and on the new width and height
*
* @param {*} image The imageData to scale
* @param {*} width The new width of the imageData
* @param {*} height The new height of the imageData
* @param {*} algorithm Scaling algorithm chosen by the user in the dialogue
*/
function resizeImageData (image, width, height, algorithm) {
algorithm = algorithm || 'bilinear-interpolation'
let resize;
switch (algorithm) {
case 'nearest-neighbor': resize = nearestNeighbor; break
case 'bilinear-interpolation': resize = bilinearInterpolation; break
default: return image;
}
const result = new ImageData(width, height)
resize(image, result)
return result
}
// REFACTOR: public static method of custom ImageData wrapper (PixelImageData?)?
/** Gets the position in (x, y) format of the pixel with index "index"
*
* @param {*} index The index of the pixel of which we need the (x, y) position
*/
function getPixelPosition(index) {
let linearIndex = index / 4;
let x = linearIndex % layers[0].canvasSize[0];
let y = Math.floor(linearIndex / layers[0].canvasSize[0]);
return [Math.ceil(x), Math.ceil(y)];
}