Do you know how each of the red, green, and blue channels is calculated when opacity of a layer is used please?

I am wondering if it is, if opacity is expressed as a value p in the range 0.0 to 1.0, if there are n layers, as

x = p * x(i) + (1 - p) * x(i - 1)

Alas, I cannot use square brackets, as the forum software treats them as markup.

and recursively back to the background colour x[0]..

In my picture, a few posts back, (r, g, b) for the blue background is (128, 128, 255) at 100% opacity.

Then each of the five yellow areas have (r, g, b) as (255, 255, 0) at 20% opacity, so p=0.2.

So if my guess at the formula is correct, then

(r, g, b) for the single yellow layer on the blue would be about (153, 153, 204)

Using Paint to look at what is the colour gives (153, 153, 204), so it looks like my guess at the formula might be correct, at least for just one semi-opaque layer upon an opaque layer.

William

The original is landscape A3 size at 300 dots per inch, plus bleed areas.

I did not include the bleed areas when exporting the png image file.

I use one seventh size because the original is 3508 pixels in height, after rounding up the original millimetre-specified A3 size after changing to using pixels as the measurement units when producing an artwork, so using 501 pixels as the height of the png image is a convenient size for use on the web in discussions such as in this thread.

William

Thank you.

William

Drilling a triangular hole

https://www.youtube.com/shorts/Qm64fTtSLcw

I already have five A3 size pictures for the art show.

Today I tried experimenting with opacity in Affinity Designer, and so I used a landscape A3 plus bleed areas electronic canvas, just in case I might want to use any result it in the art show.

This is a one-seventh both horizontally and vertically png image of what I have got so far.

The sunlight effect is produced using a full width borderless yellow filled rectangle 600 pixels high at 20% opacity and then four copies of it are placed, each with a y position 100 pixels lower down the canvas than the previous one.

Clicking on the image should produce an enlarged display.

https://i.postimg.cc/WqV07dh6/sunlight3.png

Spaghetti structure supporting bricks

https://www.youtube.com/shorts/Tsef_fg0Dns

Fitting a sphere inside a cube

https://www.youtube.com/shorts/8sn_xX8UZZU

Amazing Ave Maria (public piano, Schubert) @ station Nijmegen, the Netherlands

https://www.youtube.com/watch?v=sTsHWbqkyxI

59

(1 replies, posted in Art & Literature)

Painting a large picture

https://www.youtube.com/shorts/Gz8Aut_DiXM

60

(2 replies, posted in General Discussion)

the video wrote:

Can you play LIBIAMO ?

https://www.youtube.com/shorts/0fYZs_tyEiY

It states that the full version is on their YouTube channel, but I have not found it yet.

Can anyone find it please?

61

(2 replies, posted in General Discussion)

Well, I saw it, thought it interesting and put the link in the hope that some readers might enjoy the surprise.

If I write up every link it can spoil the enjoyment of seeing the video without a pre-description.

I remember a television presenter saying, before an episode of Alias Smith and Jones, "And now a case of Confederate money for alias Smith and Jones" and it was only in the final five minutes of the programme that the fact the box of money for which they had searched and eventually found was full of Confederate banknotes, and thus, at the time in which the story was set, worthless.

I got to the stage of turning off the sound of the television before the start of programmes due to the way a lot of announcers would spoil enjoyment of a programme by their comments before the programme started.

I post links that I find interesting, within a general thread heading, as here.

William

62

(2 replies, posted in General Discussion)

the video wrote:

Can you play La Foule of Edith Piaf? Please ...

https://www.youtube.com/shorts/J1vOylv2RM4


Edith Piaf sings La Foule

https://www.youtube.com/watch?v=Fgn8gZHJZzA

https://fr.wikipedia.org/wiki/La_Foule_(chanson)

La Foule translates into English as The Crowd.

63

(2 replies, posted in Art & Literature)

I suppose that it was another way of putting the message of this song that it is better to be free to fly than to live in a golden cage.

https://www.youtube.com/watch?v=2g6bQ6Jug5I

https://genius.com/Mireille-mathieu-der … hen-lyrics

https://translate.google.com/?sl=de& … =translate

Though if one is hard up, cold and hungry, maybe the metaphorical golden cage in a palace with everything being provided is a good choice.

64

(2 replies, posted in Art & Literature)

Videp title wrote:

Mondrian at Tate Liverpool and Turner Contemporary

https://www.youtube.com/watch?v=dhv3_nGfETw

4 minutes 33 seconds

Is that time a coincidence?

https://www.youtube.com/watch?v=AWVUp12XPpU

65

(2 replies, posted in Art & Literature)

An interesting video

https://www.youtube.com/shorts/dWKE1IFfnHk

66

(1 replies, posted in Mathematics & Science)

https://www.youtube.com/shorts/I81AwslVjkw

67

(1 replies, posted in Mathematics & Science)

https://www.youtube.com/shorts/k_Rj_irGFGg

68

(2 replies, posted in General Discussion)

https://www.youtube.com/shorts/HfYQMgPrKZ8

69

(1 replies, posted in Art & Literature)

Printing letterpress with three different colours simultaneously

https://www.youtube.com/shorts/W9hSZc-JV_w

Normally, with letterpress printing, such a task would be done with three impressions, one for each colour, with just the type for the particular colour being used at the time, yet keeping the overall layout, substituting spaces for the type unused for a particular colour, so as to achieve the desired alignment.

70

(2 replies, posted in Art & Literature)

A wider version from later.

Over at the right of the picture, is that a rabatment and then a golden ratio within it?


https://i.postimg.cc/f3YNKxBN/quasi-Mondrian2-20241031-Thursday.png

71

(2 replies, posted in Art & Literature)

Influenced by a famous artist?


https://i.postimg.cc/VSym9mbS/quasi-Mondrian-20241031-Thursday.png

Please click on the image to enlarge it.

Clicking again enlarges further.

Thank you for replying.

When I tried it with an earlier version of this PDF document during development I found that the symbol would not show, even though the font was available on the computer. It was expressed using a glyph in a font.

The lettering was fine. So I wondered if the issue was the symbol being in the Private Use Area, or perhaps simply having a code point greater than 255.

So I converted it to curves, and, knowing that other users might well not have the Sonnet to a Renaissance Lady font installed on their computer, I converted the text to curves as well, in case that might be an issue.

Also, as the image in the PDF document is a vector image, although grouped in the Affinity document, seems not to be grouped in the PDF document.

I included in the design a borderless, filled white, rectangle behind the design so as to indicate the edges of the picture.

William

The third post in this thread has the following text, and a PDF document.

William wrote:

Please find attached a PDF document.

This PDF document is designed to give a good full screen display on a display that has a 16 to 9 aspect ratio, yet is displaying an A3 size artwork.

An experiment that I have tried, and got to work, is to extract the picture and export it as an A3 size PDF document with 3 millimetre bleed areas at 300 dots per inch.

I found that an interesting experiment to do. I would be interested to know of the experiences of any reader here if the experiment is tried.

The PDF document is listed as exported from Affinity Publisher. The artwork and setting up the document was done in Affinity Designer, but I wanted to include my name as Author in the PDF document properties list.

William

At the time of writing of this post, the view count is 401 yet there are only 7 views of the PDF document, of which 2 are me testing that the upload worked fine.

I am wondering why there are so few views of the PDF document. I appreciate that some of the views of the thread may be from Bots, yet 5 views of the PDF document seems very low.

Are people wary of opening a PDF document from a post in a website?

I find it strange that people read the thread yet do not look at the PDF document?

Alas, nobody has written about their experience of trying to extract the A3 picture from the PDF document. Maybe nobody has tried.

William

https://punster.me/serif/viewtopic.php?pid=5927#p5927

So the second sonnet starts the same, then differs later.

William