Place image to alpha channels in canvas
1
I need to find top, left, max width and max height values of all transparent places in canvas.
http://jsfiddle.net/alperxx/t521jra4/ (fiddle)
I have 4 transparent place in canvas. but i can't detect true places. First alpha channel corners colour must be red. Next is: black, yellow and green. But my groups is not correct.
If I complete the groups truely, every uploading photos will place to alpha places.
My Processes are in comment.
function alphaRatio(ctx) {
var pixelData = ctx.getImageData(0, 0, ctx.canvas.width, ctx.canvas.height);
const data = pixelData.data;
const pixel_groups = ;
var total = 0;
for (let i = 0, dx = 0; dx < data.length; i++, dx = i << 2) {
if (data[dx + 3] == 0) {
//First, I'm catching all transparent pixels.
total++;
var x = (dx / 4) % ctx.canvas.width;
var y = ~~((dx / 4) / ctx.canvas.width);
// if pixel after a last grouped item add to in.
var found = false;
if (pixel_groups.length) {
for (im = 0; im < pixel_groups.length; im++) {
last_pixels = pixel_groups[im][pixel_groups[im].length - 1];
if (
last_pixels.x + 1 == x || last_pixels.x - 1 == x ||
last_pixels.y + 1 == y || last_pixels.y - 1 == y
) {
found = true;
pixel_groups[im].push({
x: x,
y: y
});
break;
}
}
}
if (!found) {
pixel_groups.push([{
x: x,
y: y
}]);
}
}
}
// i grouped all them
if (pixel_groups.length) {
console.debug(pixel_groups);
for (i = 0; i < pixel_groups.length; i++) {
var alphawidth = {};
var alphaheight = {};
for (im = 0; im < pixel_groups[i].length; im++) {
//now lets calculate first pixel left and top for width and height
if (typeof(alphawidth['min']) === 'undefined') {
alphawidth['min'] = pixel_groups[i][im].x;
alphawidth['max'] = pixel_groups[i][im].x;
} else {
if (pixel_groups[i][im].x < alphawidth['min']) {
alphawidth['min'] = pixel_groups[i][im].x;
}
if (pixel_groups[i][im].x > alphawidth['max']) {
alphawidth['max'] = pixel_groups[i][im].x;
}
}
if (typeof(alphaheight['min']) === 'undefined') {
alphaheight['min'] = pixel_groups[i][im].y;
alphaheight['max'] = pixel_groups[i][im].y;
} else {
if (pixel_groups[i][im].y < alphaheight['min']) {
alphaheight['min'] = pixel_groups[i][im].y;
}
if (pixel_groups[i][im].y > alphaheight['max']) {
alphaheight['max'] = pixel_groups[i][im].y;
}
}
}
// update group key for only x y w h
pixel_groups[i] = {
x: pixel_groups[i][0].x,
y: pixel_groups[i][0].y,
w: alphawidth['max'] - alphawidth['min'],
h: alphaheight['max'] - alphaheight['min']
};
}
// for test alpha places put a colour all corners
for (i = 0; i < pixel_groups.length; i++) {
var colour = ['red', 'black', 'yellow', 'green'];
canvas.add(new fabric.Circle({
left: pixel_groups[i].x,
top: pixel_groups[i].y,
radius: 4,
fill: colour[i],
originX: 'center',
originY: 'center',
hasControls: false
}));
canvas.add(new fabric.Circle({
left: pixel_groups[i].x + pixel_groups[i].w,
top: pixel_groups[i].y + pixel_groups[i].h,
radius: 4,
fill: colour[i],
originX: 'center',
originY: 'center',
hasControls: false
}));
canvas.add(new fabric.Circle({
left: pixel_groups[i].x + pixel_groups[i].w,
top: pixel_groups[i].y,
radius: 4,
fill: colour[i],
originX: 'center',
originY: 'center',
hasControls: false
}));
canvas.add(new fabric.Circle({
left: pixel_groups[i].x,
top: pixel_groups[i].y + pixel_groups[i].h,
radius: 4,
fill: colour[i],
originX: 'center',
originY: 'center',
hasControls: false
}));
}
return pixel_groups;
}
return false;
}
javascript canvas fabricjs alpha-transparency
asked Nov 21 '18 at 19:53
formedyaformedya
1629
add a comment |
1
I need to find top, left, max width and max height values of all transparent places in canvas.
http://jsfiddle.net/alperxx/t521jra4/ (fiddle)
I have 4 transparent place in canvas. but i can't detect true places. First alpha channel corners colour must be red. Next is: black, yellow and green. But my groups is not correct.
If I complete the groups truely, every uploading photos will place to alpha places.
My Processes are in comment.
function alphaRatio(ctx) {
var pixelData = ctx.getImageData(0, 0, ctx.canvas.width, ctx.canvas.height);
const data = pixelData.data;
const pixel_groups = ;
var total = 0;
for (let i = 0, dx = 0; dx < data.length; i++, dx = i << 2) {
if (data[dx + 3] == 0) {
//First, I'm catching all transparent pixels.
total++;
var x = (dx / 4) % ctx.canvas.width;
var y = ~~((dx / 4) / ctx.canvas.width);
// if pixel after a last grouped item add to in.
var found = false;
if (pixel_groups.length) {
for (im = 0; im < pixel_groups.length; im++) {
last_pixels = pixel_groups[im][pixel_groups[im].length - 1];
if (
last_pixels.x + 1 == x || last_pixels.x - 1 == x ||
last_pixels.y + 1 == y || last_pixels.y - 1 == y
) {
found = true;
pixel_groups[im].push({
x: x,
y: y
});
break;
}
}
}
if (!found) {
pixel_groups.push([{
x: x,
y: y
}]);
}
}
}
// i grouped all them
if (pixel_groups.length) {
console.debug(pixel_groups);
for (i = 0; i < pixel_groups.length; i++) {
var alphawidth = {};
var alphaheight = {};
for (im = 0; im < pixel_groups[i].length; im++) {
//now lets calculate first pixel left and top for width and height
if (typeof(alphawidth['min']) === 'undefined') {
alphawidth['min'] = pixel_groups[i][im].x;
alphawidth['max'] = pixel_groups[i][im].x;
} else {
if (pixel_groups[i][im].x < alphawidth['min']) {
alphawidth['min'] = pixel_groups[i][im].x;
}
if (pixel_groups[i][im].x > alphawidth['max']) {
alphawidth['max'] = pixel_groups[i][im].x;
}
}
if (typeof(alphaheight['min']) === 'undefined') {
alphaheight['min'] = pixel_groups[i][im].y;
alphaheight['max'] = pixel_groups[i][im].y;
} else {
if (pixel_groups[i][im].y < alphaheight['min']) {
alphaheight['min'] = pixel_groups[i][im].y;
}
if (pixel_groups[i][im].y > alphaheight['max']) {
alphaheight['max'] = pixel_groups[i][im].y;
}
}
}
// update group key for only x y w h
pixel_groups[i] = {
x: pixel_groups[i][0].x,
y: pixel_groups[i][0].y,
w: alphawidth['max'] - alphawidth['min'],
h: alphaheight['max'] - alphaheight['min']
};
}
// for test alpha places put a colour all corners
for (i = 0; i < pixel_groups.length; i++) {
var colour = ['red', 'black', 'yellow', 'green'];
canvas.add(new fabric.Circle({
left: pixel_groups[i].x,
top: pixel_groups[i].y,
radius: 4,
fill: colour[i],
originX: 'center',
originY: 'center',
hasControls: false
}));
canvas.add(new fabric.Circle({
left: pixel_groups[i].x + pixel_groups[i].w,
top: pixel_groups[i].y + pixel_groups[i].h,
radius: 4,
fill: colour[i],
originX: 'center',
originY: 'center',
hasControls: false
}));
canvas.add(new fabric.Circle({
left: pixel_groups[i].x + pixel_groups[i].w,
top: pixel_groups[i].y,
radius: 4,
fill: colour[i],
originX: 'center',
originY: 'center',
hasControls: false
}));
canvas.add(new fabric.Circle({
left: pixel_groups[i].x,
top: pixel_groups[i].y + pixel_groups[i].h,
radius: 4,
fill: colour[i],
originX: 'center',
originY: 'center',
hasControls: false
}));
}
return pixel_groups;
}
return false;
}
javascript canvas fabricjs alpha-transparency
asked Nov 21 '18 at 19:53
formedyaformedya
1629
add a comment |
1
1
1
I need to find top, left, max width and max height values of all transparent places in canvas.
http://jsfiddle.net/alperxx/t521jra4/ (fiddle)
I have 4 transparent place in canvas. but i can't detect true places. First alpha channel corners colour must be red. Next is: black, yellow and green. But my groups is not correct.
If I complete the groups truely, every uploading photos will place to alpha places.
My Processes are in comment.
function alphaRatio(ctx) {
var pixelData = ctx.getImageData(0, 0, ctx.canvas.width, ctx.canvas.height);
const data = pixelData.data;
const pixel_groups = ;
var total = 0;
for (let i = 0, dx = 0; dx < data.length; i++, dx = i << 2) {
if (data[dx + 3] == 0) {
//First, I'm catching all transparent pixels.
total++;
var x = (dx / 4) % ctx.canvas.width;
var y = ~~((dx / 4) / ctx.canvas.width);
// if pixel after a last grouped item add to in.
var found = false;
if (pixel_groups.length) {
for (im = 0; im < pixel_groups.length; im++) {
last_pixels = pixel_groups[im][pixel_groups[im].length - 1];
if (
last_pixels.x + 1 == x || last_pixels.x - 1 == x ||
last_pixels.y + 1 == y || last_pixels.y - 1 == y
) {
found = true;
pixel_groups[im].push({
x: x,
y: y
});
break;
}
}
}
if (!found) {
pixel_groups.push([{
x: x,
y: y
}]);
}
}
}
// i grouped all them
if (pixel_groups.length) {
console.debug(pixel_groups);
for (i = 0; i < pixel_groups.length; i++) {
var alphawidth = {};
var alphaheight = {};
for (im = 0; im < pixel_groups[i].length; im++) {
//now lets calculate first pixel left and top for width and height
if (typeof(alphawidth['min']) === 'undefined') {
alphawidth['min'] = pixel_groups[i][im].x;
alphawidth['max'] = pixel_groups[i][im].x;
} else {
if (pixel_groups[i][im].x < alphawidth['min']) {
alphawidth['min'] = pixel_groups[i][im].x;
}
if (pixel_groups[i][im].x > alphawidth['max']) {
alphawidth['max'] = pixel_groups[i][im].x;
}
}
if (typeof(alphaheight['min']) === 'undefined') {
alphaheight['min'] = pixel_groups[i][im].y;
alphaheight['max'] = pixel_groups[i][im].y;
} else {
if (pixel_groups[i][im].y < alphaheight['min']) {
alphaheight['min'] = pixel_groups[i][im].y;
}
if (pixel_groups[i][im].y > alphaheight['max']) {
alphaheight['max'] = pixel_groups[i][im].y;
}
}
}
// update group key for only x y w h
pixel_groups[i] = {
x: pixel_groups[i][0].x,
y: pixel_groups[i][0].y,
w: alphawidth['max'] - alphawidth['min'],
h: alphaheight['max'] - alphaheight['min']
};
}
// for test alpha places put a colour all corners
for (i = 0; i < pixel_groups.length; i++) {
var colour = ['red', 'black', 'yellow', 'green'];
canvas.add(new fabric.Circle({
left: pixel_groups[i].x,
top: pixel_groups[i].y,
radius: 4,
fill: colour[i],
originX: 'center',
originY: 'center',
hasControls: false
}));
canvas.add(new fabric.Circle({
left: pixel_groups[i].x + pixel_groups[i].w,
top: pixel_groups[i].y + pixel_groups[i].h,
radius: 4,
fill: colour[i],
originX: 'center',
originY: 'center',
hasControls: false
}));
canvas.add(new fabric.Circle({
left: pixel_groups[i].x + pixel_groups[i].w,
top: pixel_groups[i].y,
radius: 4,
fill: colour[i],
originX: 'center',
originY: 'center',
hasControls: false
}));
canvas.add(new fabric.Circle({
left: pixel_groups[i].x,
top: pixel_groups[i].y + pixel_groups[i].h,
radius: 4,
fill: colour[i],
originX: 'center',
originY: 'center',
hasControls: false
}));
}
return pixel_groups;
}
return false;
}
javascript canvas fabricjs alpha-transparency
asked Nov 21 '18 at 19:53
formedyaformedya
1629
I need to find top, left, max width and max height values of all transparent places in canvas.
http://jsfiddle.net/alperxx/t521jra4/ (fiddle)
I have 4 transparent place in canvas. but i can't detect true places. First alpha channel corners colour must be red. Next is: black, yellow and green. But my groups is not correct.
If I complete the groups truely, every uploading photos will place to alpha places.
My Processes are in comment.
function alphaRatio(ctx) {
var pixelData = ctx.getImageData(0, 0, ctx.canvas.width, ctx.canvas.height);
const data = pixelData.data;
const pixel_groups = ;
var total = 0;
for (let i = 0, dx = 0; dx < data.length; i++, dx = i << 2) {
if (data[dx + 3] == 0) {
//First, I'm catching all transparent pixels.
total++;
var x = (dx / 4) % ctx.canvas.width;
var y = ~~((dx / 4) / ctx.canvas.width);
// if pixel after a last grouped item add to in.
var found = false;
if (pixel_groups.length) {
for (im = 0; im < pixel_groups.length; im++) {
last_pixels = pixel_groups[im][pixel_groups[im].length - 1];
if (
last_pixels.x + 1 == x || last_pixels.x - 1 == x ||
last_pixels.y + 1 == y || last_pixels.y - 1 == y
) {
found = true;
pixel_groups[im].push({
x: x,
y: y
});
break;
}
}
}
if (!found) {
pixel_groups.push([{
x: x,
y: y
}]);
}
}
}
// i grouped all them
if (pixel_groups.length) {
console.debug(pixel_groups);
for (i = 0; i < pixel_groups.length; i++) {
var alphawidth = {};
var alphaheight = {};
for (im = 0; im < pixel_groups[i].length; im++) {
//now lets calculate first pixel left and top for width and height
if (typeof(alphawidth['min']) === 'undefined') {
alphawidth['min'] = pixel_groups[i][im].x;
alphawidth['max'] = pixel_groups[i][im].x;
} else {
if (pixel_groups[i][im].x < alphawidth['min']) {
alphawidth['min'] = pixel_groups[i][im].x;
}
if (pixel_groups[i][im].x > alphawidth['max']) {
alphawidth['max'] = pixel_groups[i][im].x;
}
}
if (typeof(alphaheight['min']) === 'undefined') {
alphaheight['min'] = pixel_groups[i][im].y;
alphaheight['max'] = pixel_groups[i][im].y;
} else {
if (pixel_groups[i][im].y < alphaheight['min']) {
alphaheight['min'] = pixel_groups[i][im].y;
}
if (pixel_groups[i][im].y > alphaheight['max']) {
alphaheight['max'] = pixel_groups[i][im].y;
}
}
}
// update group key for only x y w h
pixel_groups[i] = {
x: pixel_groups[i][0].x,
y: pixel_groups[i][0].y,
w: alphawidth['max'] - alphawidth['min'],
h: alphaheight['max'] - alphaheight['min']
};
}
// for test alpha places put a colour all corners
for (i = 0; i < pixel_groups.length; i++) {
var colour = ['red', 'black', 'yellow', 'green'];
canvas.add(new fabric.Circle({
left: pixel_groups[i].x,
top: pixel_groups[i].y,
radius: 4,
fill: colour[i],
originX: 'center',
originY: 'center',
hasControls: false
}));
canvas.add(new fabric.Circle({
left: pixel_groups[i].x + pixel_groups[i].w,
top: pixel_groups[i].y + pixel_groups[i].h,
radius: 4,
fill: colour[i],
originX: 'center',
originY: 'center',
hasControls: false
}));
canvas.add(new fabric.Circle({
left: pixel_groups[i].x + pixel_groups[i].w,
top: pixel_groups[i].y,
radius: 4,
fill: colour[i],
originX: 'center',
originY: 'center',
hasControls: false
}));
canvas.add(new fabric.Circle({
left: pixel_groups[i].x,
top: pixel_groups[i].y + pixel_groups[i].h,
radius: 4,
fill: colour[i],
originX: 'center',
originY: 'center',
hasControls: false
}));
}
return pixel_groups;
}
return false;
}
javascript canvas fabricjs alpha-transparency
javascript canvas fabricjs alpha-transparency
asked Nov 21 '18 at 19:53
formedyaformedya
1629
asked Nov 21 '18 at 19:53
formedyaformedya
1629
edited Nov 28 '18 at 13:30
formedya
asked Nov 21 '18 at 19:53
formedyaformedya
1629
asked Nov 21 '18 at 19:53
formedyaformedya
1629
asked Nov 21 '18 at 19:53
formedyaformedya
1629
1629
add a comment |
add a comment |
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