The filter mixin adds functionality to Cell, Group and all entity factories which allows those objects to use Scrawl-canvas Filter objects in their output.
import { asset, filter, styles } from '../core/library.js';
import { generateUuid, mergeOver, removeItem, Ωempty } from '../helper/utilities.js';
import { checkForWorkstoreItem, setWorkstoreItem } from '../helper/workstore.js';
import { releaseCell, requestCell } from '../untracked-factory/cell-fragment.js';Shared constants
import { _floor, _isArray, _max, _min, BLANK, BOTTOM, CENTER, LEFT, NONE, PROCESS_IMAGE, RIGHT, SOURCE_OVER, T_FILTER, T_IMAGE, TOP, ZERO_STR } from '../helper/shared-vars.js';Local constants
const CONTAIN = 'contain',
COVER = 'cover',
STRETCH = 'stretch',
CHECK_POS_X = [LEFT, CENTER, RIGHT],
CHECK_POS_Y = [TOP, CENTER, BOTTOM];export default function (P = Ωempty) {All factories using the filter mixin will add these attributes to their objects
const defaultAttributes = {filters - An array of filter object String names. If only one filter is to be applied, then it is enough to use the String name of that filter object - Scrawl-canvas will make sure it gets added to the Array.
addFilters and removeFilters functions. Note that the set function will replace all the existing filters in the array with the new filters. To remove all existing filters from the array, use the clearFilters function filters: null,isStencil - Use the entity as a stencil. When this flag is set filter effects will be applied to the background imagery covered by the entity (or Group of entitys, or Cell), the results of which will replace the entity/Group/Cell in the final display.
isStencil: false,memoizeFilterOutput - SC uses memoization as a means to enhance the speed of filter application. When an entity has filters sety on it, and the memoizeFilterOutput flag is set to true, the filter engine will cache the generated output after its first run and, for subsequent Display cycles, serve up the cached result rather than perform the filter calculations again. Things to note:
filters array, or when the attributes of a filter in the array update.isStencil flag is set to true the memoizeFilterOutput flag is ignored. memoizeFilterOutput: false,
};
P.defs = mergeOver(P.defs, defaultAttributes); const S = P.setters;filters - _Dangerous action! - replaces the existing filters Array with a new filters Array. If a string name is supplied, will add that name to the existing filters array
S.filters = function (item) {
if (item) {
this.filters.length = 0;
if (!_isArray(item)) item = [item];
item.forEach(f => {
if (f.substring) this.filters.push(f);
else if (f.type === T_FILTER) this.filters.push(f.name);
}, this);
this.dirtyFilters = true;
this.dirtyImageSubscribers = true;
this.dirtyFilterIdentifier = true;
}
};memoizeFilterOutput
S.memoizeFilterOutput = function (item) {
this.memoizeFilterOutput = item;
this.updateFilterIdentifier(!!item);
};updateFilterIdentifier - manually trigger re-memoization. The function’s (optional) argument is a boolean.
P.updateFilterIdentifier = function (item) {
this.dirtyFilterIdentifier = false;
if (this.state) this.state.dirtyFilterIdentifier = false;
if (this.memoizeFilterOutput && item) this.filterIdentifier = generateUuid();
else this.filterIdentifier = ZERO_STR;
};cleanFilters - Internal housekeeping
order attribute. They will be processed in the order in which they appear in the filters Array. P.cleanFilters = function () {
this.dirtyFilters = false;
this.dirtyFiltersCache = true;
const {filters, currentFilters} = this;
currentFilters.length = 0;
filters.forEach(f => {
if (f.substring) {
const obj = filter[f];
if (obj) currentFilters.push(obj);
}
else if (f && f.type && f.type === T_FILTER) currentFilters.push(f);
});
};addFilters, removeFilters - Add or remove one or more filter name strings to/from the filters array. Filter name strings, or the filter objects themselves, can be supplied as comma-separated arguments to the function.
filters array. If the filters need to be reordered, use the set functionality instead to replace the array with an array containing the desired filter order P.addFilters = function (...args) {
args.forEach(f => {
if (f && f.type === T_FILTER) f = f.name;
this.filters.push(f);
}, this);
this.dirtyFilters = true;
this.dirtyImageSubscribers = true;
this.dirtyFilterIdentifier = true;
return this;
};
P.removeFilters = function (...args) {
args.forEach(f => {
if (f && f.type === T_FILTER) f = f.name;
removeItem(this.filters, f);
}, this);
this.dirtyFilters = true;
this.dirtyImageSubscribers = true;
this.dirtyFilterIdentifier = true;
return this;
};clearFilters - Clears the filters array
P.clearFilters = function () {
this.filters.length = 0;
this.dirtyFilters = true;
this.dirtyImageSubscribers = true;
this.dirtyFilterIdentifier = true;
return this;
};hasFilters - A quick check to see if any filters have been assigned to this artefact
P.hasFilters = function () {
return !!this.filters.length;
};preprocessFilters - internal function called as part of the Display cycle.
P.preprocessFilters = function (filters, hostWidth, hostHeight) {
for (let i = 0, iz = filters.length, filter; i < iz; i++) {
filter = filters[i];
for (let j = 0, jz = filter.actions.length, obj; j < jz; j++) {
obj = filter.actions[j];Currently only the process-image filter action requires pre-processing
if (obj.action === PROCESS_IMAGE) this.preprocessImageFilter(obj, hostWidth, hostHeight)
}
if (filter.dirtyFilterIdentifier) this.dirtyFilterIdentifier = true;
}
const state = this.state;
if (state) {
if (state.dirtyFilterIdentifier) this.dirtyFilterIdentifier = true;
else {
const {fillStyle, strokeStyle} = state;
if (styles[fillStyle] && styles[fillStyle].dirtyFilterIdentifier) this.dirtyFilterIdentifier = true;
else if (styles[strokeStyle] && styles[strokeStyle].dirtyFilterIdentifier) this.dirtyFilterIdentifier = true;
}
}
if (this.dirtyFilterIdentifier || (this.state && this.state.dirtyFilterIdentifier)) this.updateFilterIdentifier(true);
};preprocessImageFilter - pre-process images ready to be used in the filter engine.
P.preprocessImageFilter = function (obj, hostWidth, hostHeight) {
const img = asset[obj.asset];Only continue if the image already exists as an asset
if (img) {
let width, height, snd, cnd,
copyStartX, copyStartY, copyWidth, copyHeight,
fit, scale, smoothing, backgroundColor,
positionX, positionY, offsetX, offsetY,
drawWidth, drawHeight, dx, dy;Any asset can be used as an “image”, but given assets can be animated we do a check.
if (T_IMAGE !== img.type) {
img.checkSource();
obj.identifier = `user-image-${obj.asset}-${generateUuid()}`;
this.dirtyFilterIdentifier = true;
}
const specifiedIdentifier = `${obj.identifier}_${hostWidth}_${hostHeight}`;We pre-process when the image doesn’t already exist in the Workstore. The identifier attribute is set by the process-image filter action
process-image has been set up as a legacy method filter, not the modern actions filteractions approach, the identifier attribute needs to be created and updated (to break cache) manually, un user code. if (!checkForWorkstoreItem(specifiedIdentifier)) {
width = img.sourceNaturalWidth;
height = img.sourceNaturalHeight;
snd = img.sourceNaturalDimensions;
cnd = img.currentDimensions;Dimensions values:
hostWidth, hostHeight - received by the function as arguments, representing the area within which the ingested image will sitwidth, height - calculated from image attributes if (!width || !height) {
if (snd && snd[0] && snd[1]) {
width = width || snd[0];
height = height || snd[1];
}
else if (cnd && cnd[0] && cnd[1]) {
width = width || cnd[0];
height = height || cnd[1];
}
}Proceed if we have the image dimensions, otherwise do nothing
0 or undefined. if (width && height) {copyX and copyY are deprecated names for the copyStartX and copyStartY attributes. Check for them here
copyStartX = (obj.copyStartX != null) ? obj.copyStartX : obj.copyX;
copyStartY = (obj.copyStartY != null) ? obj.copyStartY : obj.copyY;Don’t assume the copy attributes have been set. Defaults are to use the entire image in the following functionality
copyStartX = (copyStartX != null) ? copyStartX : 0;
copyStartY = (copyStartY != null) ? copyStartY : 0;
copyWidth = (obj.copyWidth != null) ? obj.copyWidth : '100%';
copyHeight = (obj.copyHeight != null) ? obj.copyHeight : '100%';De-stringify start attributes
if (copyStartX.substring) copyStartX = (parseFloat(copyStartX) / 100) * width;
if (copyStartY.substring) copyStartY = (parseFloat(copyStartY) / 100) * height;Work with integers
copyStartX = _floor(copyStartX);
copyStartY = _floor(copyStartY);Correct start positions, which must be within the image dimensions
if (copyStartX < 0) copyStartX = 0;
else if (copyStartX >= width) copyStartX = width - 1;
if (copyStartY < 0) copyStartY = 0;
else if (copyStartY >= height) copyStartY = height - 1;Correct copy dimensions
if (copyWidth.substring) copyWidth = (parseFloat(copyWidth) / 100) * width;
if (copyHeight.substring) copyHeight = (parseFloat(copyHeight) / 100) * height;Work with integers
copyWidth = _floor(copyWidth);
copyHeight = _floor(copyHeight);Correct copy dimensions
if (copyWidth < 1) copyWidth = 1;
if (copyHeight < 1) copyHeight = 1;
if (copyWidth > width) copyWidth = width;
if (copyHeight > height) copyHeight = height;If start + copy dimension is greater than the image dimension, then we correct the start value (to prevent unexpected stretching of the copy output)
if (copyStartX + copyWidth > width) copyStartX = width - copyWidth;
if (copyStartY + copyHeight > height) copyStartY = height - copyHeight;Collect the process-image filter action’s other attributes:
fit: string - values ‘contain’, ‘cover’, ‘stretch’, ‘none’smoothing: boolean fit = (obj.fit != null) ? obj.fit : NONE;
smoothing = (obj.smoothing != null) ? obj.smoothing : false;When the desired image copy is smaller than the host, we fill in the background with a color
rgb(0 0 0 / 0)) for images that will be used with the composite filter actionrgb(127 127 127 / 0.5)) for images to be used with the displace filter action - half-transparent gray values should prevent pixels from moving unexpectedlyblend filter action, be aware that the background color can have an effect on the blended results; transparent pixels are ignored but if other filter actions modify the image data prior to it reaching the blend action then the color of the pixel may have an effect backgroundColor = (obj.backgroundColor != null) ? obj.backgroundColor : BLANK; const src = img.source || img.element;
if (src) {
const mycell = requestCell(),
engine = mycell.engine,
canvas = mycell.element;
canvas.width = hostWidth;
canvas.height = hostHeight;
engine.resetTransform();
engine.globalCompositeOperation = SOURCE_OVER;
engine.globalAlpha = 1;
engine.imageSmoothingEnabled = smoothing;
engine.clearRect(0, 0, hostWidth, hostHeight);
if (backgroundColor && backgroundColor !== BLANK) {
engine.fillStyle = backgroundColor;
engine.fillRect(0, 0, hostWidth, hostHeight);
}Copy the image into the Cell
switch (fit) {
case CONTAIN: {
scale = _min(hostWidth / copyWidth, hostHeight / copyHeight);
drawWidth = copyWidth * scale;
drawHeight = copyHeight * scale;
drawWidth = _max(1, _floor(drawWidth));
drawHeight = _max(1, _floor(drawHeight));
dx = ((hostWidth - drawWidth) / 2) | 0;
dy = ((hostHeight - drawHeight) / 2) | 0;
engine.drawImage(
src,
copyStartX, copyStartY, copyWidth, copyHeight,
dx, dy, drawWidth, drawHeight,
);
break;
}
case COVER: {
scale = _max(hostWidth / copyWidth, hostHeight / copyHeight);
drawWidth = copyWidth * scale;
drawHeight = copyHeight * scale;
drawWidth = _max(1, _floor(drawWidth));
drawHeight = _max(1, _floor(drawHeight));
dx = ((hostWidth - drawWidth) / 2) | 0;
dy = ((hostHeight - drawHeight) / 2) | 0;
engine.drawImage(
src,
copyStartX, copyStartY, copyWidth, copyHeight,
dx, dy, drawWidth, drawHeight,
);
break;
}
case STRETCH: {
drawWidth = hostWidth;
drawHeight = hostHeight;
drawWidth = _max(1, _floor(drawWidth));
drawHeight = _max(1, _floor(drawHeight));
dx = ((hostWidth - drawWidth) / 2) | 0;
dy = ((hostHeight - drawHeight) / 2) | 0;
engine.drawImage(
src,
copyStartX, copyStartY, copyWidth, copyHeight,
dx, dy, drawWidth, drawHeight,
);
break;
}
default: {When the image is not being fitted to the output (‘contain’, ‘cover’, ‘stretch’), it can be positioned and scaled within the output instead
positionX can have values ‘left’, ‘center’ (default), ‘right’
positionX = (obj.positionX != null) ? obj.positionX : CENTER;
if (!CHECK_POS_X.includes(positionX)) positionX = CENTER;positionY can have values ‘top’, ‘center’ (default), ‘bottom’
positionY = (obj.positionY != null) ? obj.positionY : CENTER;
if (!CHECK_POS_Y.includes(positionY)) positionY = CENTER;offsetX, offsetY - either pixel numbers or string % values relative to the host dimensions
offsetX = (obj.offsetX != null) ? obj.offsetX : 0;
offsetY = (obj.offsetY != null) ? obj.offsetY : 0;
if (offsetX.substring) offsetX = (parseFloat(offsetX) / 100) * hostWidth;
if (offsetY.substring) offsetY = (parseFloat(offsetY) / 100) * hostHeight;scale
scale = (obj.scale != null) ? obj.scale : 1;
if (scale < 0.01) scale = 0.01;
drawWidth = copyWidth * scale;
drawHeight = copyHeight * scale;Calculate the start positions
if (positionX === LEFT) dx = 0;
else if (positionX === RIGHT) dx = hostWidth - drawWidth;
else dx = _floor((hostWidth / 2) - (drawWidth / 2));
dx += offsetX;
if (positionY === TOP) dy = 0;
else if (positionY === BOTTOM) dy = hostHeight - drawHeight;
else dy = _floor((hostHeight / 2) - (drawHeight / 2));
dy += offsetY;
engine.drawImage(
src,
copyStartX, copyStartY, copyWidth, copyHeight,
dx, dy, drawWidth, drawHeight,
);
}
}
setWorkstoreItem(specifiedIdentifier, engine.getImageData(0, 0, hostWidth, hostHeight));
releaseCell(mycell);
}
}
}
}
};
};