issue155:inkscape
Différences
Ci-dessous, les différences entre deux révisions de la page.
Prochaine révision | Révision précédente | ||
issue155:inkscape [2020/03/28 17:51] – créée auntiee | issue155:inkscape [2020/04/09 18:43] (Version actuelle) – andre_domenech | ||
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- | This month and next, I’m going to cover a couple of Inkscape features that have fallen through the gaps in my previous coverage. The first of these, disgracefully, | + | **This month and next, I’m going to cover a couple of Inkscape features that have fallen through the gaps in my previous coverage. The first of these, disgracefully, |
- | The Unset Paint button was eventually described in part 30 (FCM issue #90), when I covered its use with clones. But what of the “two splodges on the right of the Fill tab”? For clarity, let’s first take a look at a screenshot of the Fill and Stroke dialog, in which I’ve circled the splodges. | + | The Unset Paint button was eventually described in part 30 (FCM issue #90), when I covered its use with clones. But what of the “two splodges on the right of the Fill tab”? For clarity, let’s first take a look at a screenshot of the Fill and Stroke dialog, in which I’ve circled the splodges.** |
- | To understand what effect these splodges – which are actually a pair of mutually exclusive radio buttons – have on your objects, we’ll need a path to test with. Not just any path will do, however. These buttons have an effect only on paths that are either self-intersecting, or which contain sub-paths. Let’s deal with the former to start with: what exactly do I mean by ‘self-intersecting’? | + | Ce mois-ci et le prochain, je vais parler de quelques fonctionnalités d' |
- | Consider the paths below. The one on the left is just a simple U-shaped filled path. Nothing special, no sneaky tricks. Just 10 nodes forming a shape with a couple of arms. The shape on the right is just a duplicate of the first one, with the end of the left arm moved to the right, and the end of the right arm moved to the left, so the arms cross each other. No nodes were added or removed, they were just moved around a little. | + | Le bouton Remplissage indéfini |
- | The second shape is a self-intersecting path. It’s a closed | + | **To understand what effect these splodges – which are actually |
- | Turning | + | Consider the paths below. The one on the left is just a simple U-shaped filled path. Nothing special, no sneaky tricks. Just 10 nodes forming a shape with a couple of arms. The shape on the right is just a duplicate of the first one, with the end of the left arm moved to the right, |
- | Notice how the stroke is visible for both arms. If one crossed over the other you might expect the stroke of the arm on the bottom to be obscured by the one that’s on top, but that’s not how things work in the 2D graphics world. You’d also expect the colour of the fill to be a little darker where the two translucent arms cross over, but that’s not the case either. | + | Pour comprendre l' |
- | It’s also important to note that the arms don’t have to completely pass through each other in order to be a self intersecting shape, and that the shape could self-intersect multiple times, as demonstrated in these variations on the theme: | + | Prenez les chemins ci-dessous. Celui de gauche est un simple chemin rempli en forme de U. Rien de spécial, pas de truc insidieux. Juste 10 nœuds donnant une forme avec deux bras. La forme de droite n'est que la copie de la première, avec la terminaison gauche déplacée sur la droite et la fin du bras droit déplacé à gauche, de sorte que les bras se croisent. Aucun nœud n'a été ajouté ou enlevé ; ils ont juste été un peu déplacés. |
- | Now we’re all clear on what a self-intersecting path actually is, let’s look at how they’re affected by the splodgy radio buttons. The first thing to note is that the images so far have all been taken with the second button selected – the one that’s completely filled in. Switch to the first button, and we get this: | + | **The second shape is a self-intersecting path. It’s a closed path that is drawn such that it crosses itself, although |
- | The basic U-shaped path remains unaffected. It’s not a self-intersecting path, and it doesn’t contain any sub-paths, so the radio buttons have no effect. All the others, however, have no fill rendered in the intersecting parts. The stroke | + | Turning on the stroke |
- | This behaviour is a little confusing at first. Surely the intersecting parts are inside the shape, so they should still be filled, right? Unfortunately our intuitive idea of in-and-out doesn’t always apply in the world of computer graphics. Instead there are different rules or heuristics for determining whether a point is inside or outside a shape – and the splodgy buttons are used to switch between a couple of those rules. Let’s take a look at paths with sub-paths to try to explain why there’s a need for this choice. | + | La seconde forme est un chemin qui s' |
+ | |||
+ | En activant le contour et en diminuant l' | ||
+ | |||
+ | **Notice how the stroke is visible for both arms. If one crossed over the other you might expect the stroke of the arm on the bottom to be obscured by the one that’s on top, but that’s not how things work in the 2D graphics world. You’d also expect the colour of the fill to be a little darker where the two translucent arms cross over, but that’s not the case either. | ||
+ | |||
+ | It’s also important to note that the arms don’t have to completely pass through each other in order to be a self intersecting shape, and that the shape could self-intersect multiple times, as demonstrated in these variations on the theme:** | ||
+ | |||
+ | Notez que le contour est visible pour les deux bras. Si l'un d'eux avait croisé l' | ||
+ | |||
+ | Il est aussi important de noter que les bras ne sont pas obligés de passer complètement l'un à travers l' | ||
+ | |||
+ | **Now we’re all clear on what a self-intersecting path actually is, let’s look at how they’re affected by the splodgy radio buttons. The first thing to note is that the images so far have all been taken with the second button selected – the one that’s completely filled in. Switch to the first button, and we get this: | ||
+ | |||
+ | The basic U-shaped path remains unaffected. It’s not a self-intersecting path, and it doesn’t contain any sub-paths, so the radio buttons have no effect. All the others, however, have no fill rendered in the intersecting parts. The stroke is still drawn, but the fill isn’t.** | ||
+ | |||
+ | Maintenant que tout est clair sur ce qu'est un chemin qui s' | ||
+ | |||
+ | La forme de base en U reste inchangée. Ce n'est pas un chemin qui s' | ||
+ | |||
+ | **This behaviour is a little confusing at first. Surely the intersecting parts are inside the shape, so they should still be filled, right? Unfortunately our intuitive idea of in-and-out doesn’t always apply in the world of computer graphics. Instead there are different rules or heuristics for determining whether a point is inside or outside a shape – and the splodgy buttons are used to switch between a couple of those rules. Let’s take a look at paths with sub-paths to try to explain why there’s a need for this choice. | ||
When you look at the self-intersecting shapes above, it’s pretty obvious that the fully-filled option (second button) is the right choice most of the time. Imagine trying to draw a figure-of-eight, | When you look at the self-intersecting shapes above, it’s pretty obvious that the fully-filled option (second button) is the right choice most of the time. Imagine trying to draw a figure-of-eight, | ||
• Draw a circle for the outside. | • Draw a circle for the outside. | ||
• Draw a smaller circle for the inside. | • Draw a smaller circle for the inside. | ||
- | • Path > Combine to create a complex path, made up of two sub-paths. | + | • Path > Combine to create a complex path, made up of two sub-paths.** |
+ | |||
+ | Ce comportement est, au début, un peu troublant. Il est sûr que les parties qui se croisent sont dans la forme, aussi elles devraient être remplies, non ? Malheureusement, | ||
+ | |||
+ | Quand nous regardons les formes auto-croisées ci-dessus, il est assez évident que l' | ||
+ | ••Dessinez un cercle pour l' | ||
+ | ••Dessinez un cercle plus petit pour l' | ||
+ | ••Chemin > Combiner pour créer un chemin complexe, fait de deux sous-chemins. | ||
+ | |||
+ | **In this image (above) you can see the two separate shapes on the left, and the result of combining them in the middle. The ‘hole’ in the shape is filled – not really what we were after. Switching to the first button, however, gives the expected result, as shown in the version on the right. | ||
- | In this image (above) you can see the two separate shapes on the left, and the result of combining them in the middle. The ‘hole’ in the shape is filled – not really what we were after. Switching to the first button, however, gives the expected result, as shown in the version on the right. | ||
Now we’ve got a simple rule-of-thumb: | Now we’ve got a simple rule-of-thumb: | ||
- | On the left we have the problem of no fill in the self-intersecting part, but the hole is fine. With the right-hand button we get a fill in the self-intersecting part, but no hole. Is there any way we can have the best of both options? | + | On the left we have the problem of no fill in the self-intersecting part, but the hole is fine. With the right-hand button we get a fill in the self-intersecting part, but no hole. Is there any way we can have the best of both options?** |
- | The answer is obviously ‘yes’, but to get there it helps to understand what the two heuristics are that we’ve been switching between. The first button has a tooltip that reads “any path self-intersections or subpaths create holes in the fill”, and is referred to as the “even-odd” rule. The heuristic for this is pretty simple: | + | Dans l' |
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+ | Maintenant, nous obtenons une règle empirique simple : utiliser le bouton de gauche pour les chemins avec des sous-chemins et le bouton de droite pour les chemins qui s' | ||
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+ | Sur la gauche, le problème est l' | ||
+ | |||
+ | **The answer is obviously ‘yes’, but to get there it helps to understand what the two heuristics are that we’ve been switching between. The first button has a tooltip that reads “any path self-intersections or subpaths create holes in the fill”, and is referred to as the “even-odd” rule. The heuristic for this is pretty simple: | ||
• Pick a point in the shape. | • Pick a point in the shape. | ||
• Draw an imaginary straight line from that point out of the shape in any direction. | • Draw an imaginary straight line from that point out of the shape in any direction. | ||
Ligne 38: | Ligne 72: | ||
• If the final count is even, the point was outside the shape. If the count is odd, the point was inside the shape. | • If the final count is even, the point was outside the shape. If the count is odd, the point was inside the shape. | ||
- | By performing this for a point in each region of the shape, Inkscape can determine which areas are inside, and therefore need to be filled, and which are outside. But it does result in self-intersections being counted as outside, and left unfilled. | + | By performing this for a point in each region of the shape, Inkscape can determine which areas are inside, and therefore need to be filled, and which are outside. But it does result in self-intersections being counted as outside, and left unfilled.** |
- | The second button has a tooltip that reads “fill is solid unless a subpath is counterdirectional”, | + | La réponse est évidemment « oui », mais pour y arriver, il est préférable de comprendre ce que sont les deux heuristiques entre lesquelles nous basculons. Le premier bouton a une info-bulle qui dit « Tout auto-croisement ou sous-chemin crée un trou dans le remplissage » et elle est nommée la règle « pair-impair ». L' |
+ | ••Sélectionner un point de la forme. | ||
+ | ••Dessiner une ligne droite imaginaire à partir de ce point de la forme dans une direction quelconque. | ||
+ | ••Compter les points de croisement, en commençant à zéro. | ||
+ | ••Ajouter un au compteur chaque fois que la ligne croise une limite de chemin ou de sous-chemin. | ||
+ | ••Si le compte final est pair, le point était en dehors de la forme. Si le compte est impair, le point était à l' | ||
+ | |||
+ | En réalisant cela pour un point de chaque zone de la forme, Inkscape peut déterminer quelles sont les zones intérieures, | ||
+ | |||
+ | **The second button has a tooltip that reads “fill is solid unless a subpath is counterdirectional”, | ||
• Pick a point in the shape. | • Pick a point in the shape. | ||
• Draw an imaginary straight line from that point out of the shape in any direction. | • Draw an imaginary straight line from that point out of the shape in any direction. | ||
• Keep a ‘winding count’ which starts at zero. | • Keep a ‘winding count’ which starts at zero. | ||
• Each time the line crosses a path or sub-path, add one to the count if the path is crossing the line from left to right (clockwise from the perspective of the point) or subtract one if the path is crossing from right to left (counter-clockwise). | • Each time the line crosses a path or sub-path, add one to the count if the path is crossing the line from left to right (clockwise from the perspective of the point) or subtract one if the path is crossing from right to left (counter-clockwise). | ||
- | • If the final count is zero the point is outside the shape, otherwise it is inside. | + | • If the final count is zero the point is outside the shape, otherwise it is inside.** |
- | From this algorithm and the mention of “counterdirectional” in the tooltip – you may have already worked out that using the second splodgy button (non-zero) lets us switch sub-paths between filled and unfilled by reversing the direction of the nodes. Fortunately for us, Inkscape makes this fairly easy: | + | L' |
+ | ••Sélectionner un point dans la forme. | ||
+ | ••Dessiner une ligne droite imaginaire à partir de ce point de la forme dans une direction queconque. | ||
+ | ••Faire le compte des enroulements en commençant à zéro. | ||
+ | ••Chaque fois que la ligne croise un chemin ou un sous-chemin, | ||
+ | ••Si le résultat final est zéro, le point est en dehors de la forme ; autrement, il est interne. | ||
+ | |||
+ | **From this algorithm and the mention of “counterdirectional” in the tooltip – you may have already worked out that using the second splodgy button (non-zero) lets us switch sub-paths between filled and unfilled by reversing the direction of the nodes. Fortunately for us, Inkscape makes this fairly easy: | ||
• Select the composite path and switch to the node tool (F2). | • Select the composite path and switch to the node tool (F2). | ||
• Select a node in the sub-path. | • Select a node in the sub-path. | ||
- | • Use Path > Reverse to reverse the order of the nodes in the sub-path without changing the shape. | + | • Use Path > Reverse to reverse the order of the nodes in the sub-path without changing the shape.** |
+ | |||
+ | À partir de cet algorithme et de la mention « en sens inverse » de l' | ||
+ | ••Sélectionnez le chemin composite et passez sur l' | ||
+ | ••Sélectionnez un nœud du sous-chemin. | ||
+ | ••Utilisez Chemin > Inverser pour inverser l' | ||
+ | |||
+ | **You can see the effect of this approach in the following image. In this case I’ve also added arrow markers to the paths, to clarify what’s happening. The first image is our starting path, created by combining an oval with a self-intersecting shape. You can see from the arrows that the sub-path is running counter-clockwise. In the second image I’ve reversed the direction of the sub-path, the arrows point the opposite way, and the shape has a hole for the sub-path but not for the self-intersection. | ||
+ | |||
+ | Unfortunately this simple approach doesn’t appear to work in the beta of Inkscape v1.0, where the Path > Reverse operation reverses the entire path rather than the selected sub-path. The only option in this case is to use Path > Break Apart to split the shape down into its constituent parts, then use Path > Reverse on just one of those paths, then finally use Path > Combine to re-combine them back into your original complex path. This is a definite step backwards in the workflow, so I will be filing a bug about this on the Inkscape issue tracker.** | ||
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+ | Vous pouvez voir l' | ||
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+ | Malheureusement, | ||
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+ | **This path-reversing approach works for simple shapes where the nesting of sub-paths isn’t very deep. For more complex arrangements you may need to reverse more than one path to get the effect you want. And if there are also intersections between sub-paths, or self-intersections within them, you may never be able to get just the fill you want, no matter what you try. In those cases you may find it easiest to use the first splodge (even-odd) to fill the entire shape, then create your complex hole arrangement by clipping with a suitably constructed path. | ||
- | You can see the effect of this approach in the following image. In this case I’ve also added arrow markers to the paths, to clarify what’s happening. The first image is our starting path, created by combining an oval with a self-intersecting | + | It’s worth noting that you might never experience this problem. Punching a hole through |
- | Unfortunately this simple approach doesn’t appear | + | |
- | This path-reversing approach works for simple shapes where the nesting of sub-paths isn’t very deep. For more complex | + | Cette approche d' |
- | It’s worth noting that you might never experience this problem. Punching a hole through a shape is more commonly done using Path > Difference than Path > Combine, and the former usually results in a sub-path going in the right direction. | + | Il est intéressant de noter que vous pourriez ne jamais tomber sur ce problème. Découper un trou dans une forme est une action plus classiquement faite avec Chemin |
issue155/inkscape.1585414266.txt.gz · Dernière modification : 2020/03/28 17:51 de auntiee