Faster way to draw part of an image?

Processing Coding Questions
1

i need to be able to draw the top part of an image, here’s what i have

void drawImageSplice(PGraphics pg,PImage img,int x,int y,int w,int h,float cut){
  int yp = round(h*cut);
  if(yp>0){
    PGraphics buffer = createGraphics(w,yp);
    buffer.beginDraw();
    buffer.image(img,0,0,w,h);
    buffer.endDraw();
    pg.image(buffer,x,y,w,yp);
  }
}

this works great locally but in a live html canvas it’s very slow. is there a faster way to do this? thanks

2

The clip function may be of use, since it allows you to temporarily draw only in specific rectangle on screen

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3

oh that’s perfect thanks

4

wait apparently this doesn’t work in html at all. like it just stops the program immediately

5

it works great in local processing but in live html with a processing canvas it goes blank immediately. even just calling noClip() breaks the canvas.

image

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image1371×798 1.45 KB

6

Then an alternative which avoids making new PGraphics is the copy() method, which allows you to copy a certain rectangle of an image using the underlying pixels array. This may be more memory efficient, since you are not creating a new PGraphics every time you draw the image, but it likely isn’t much faster since you are copying pixels rather than drawing an image using image(). I haven’t tested the speed of this function, but it may be worth a shot.

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7

do you know if clip() can be used in html. i still can’t get it to run for some reason