Too outrageous, these two colors are the same?IntersectionIntersection

First of all, everyone came to see Zhang Tu together. Is there a jar of red Coca -Cola in the picture? Some people will say, I believe my eyes are true, and there must be.

Figure 1: "Red Cola can" pictures widely reposted on social media (partial amplification on the right)

Picture source: Jimhejl (Twitter)

But don't worry, after amplifying this picture on the mobile phone or computer screen, look back and look at it carefully. Do you feel something wrong? There seems to be only some black, white flowers and green lines in it, but there is no red with the eight sutras, but when the picture is reduced to the original shape, the red cola can appears again. How to explain this strange phenomenon of true and fantasy? Is it true that because there is goodness in my heart, I see all the light, there are evil in my heart, all of which are dark, there are Coca -Cola in my heart.

If the vision deceives you, don't be sad, don't be anxious, Light Popular Popularity will answer your questions in optics. A photo shows that the color of the out of nothing is actually not rare, which is related to the way the photo itself represents the color information. Whether it is a camera, a display, a printer, a projector, a variety of digital image equipment, when indicating a picture, it is in the form of a pixel array. To put it plainly, the entire picture is composed of many small squares as the basic unit. Each small square is called a pixel with its own color. Twenty or thirty years ago, the early video game console was rough and low in resolution. Each pixel size was large. The image always had a "square sense", like a mosaic. Later, with the development of display technology, the number of pixels of a picture became more, and the size of each pixel became smaller. The form of the pixel array has been maintained. Of course, driven by the retro trend, the NFT avatar represented by Cryptopunk today will still make you have a clear "pixel" (NFT professional name is Non-FUNGIBLE token, intangible homogeneity).

Figure 2: The picture of the early video game machine

Photo source: Light Popular Popularity Square/Veer

Figure 3: NFT avatar

Photo source: Light Popular Popularity Square/Veer

我们平时常说黑白照片和彩色照片，黑白电影和彩色电影，其实“黑白”指的应该是“灰度”，里面虽然没有彩色，但是具有从全黑色、深灰色，中灰色，浅灰色一直到The full white continuous transition (specifically represented by the grayscale value 0 to 255), which can also bring a considerable degree of image effects and expressiveness. Most of the screens are used with no color gray effect. But sometimes, due to technical restrictions, the real grayscale cannot be done. For example, a simple printer or display can only display all black (0) and all white (255) in each pixel, which is equivalent to only pure black and Two pure white brushes can be called a real "black and white" dual -value display. The clever woman is difficult to cook without rice. If you want to draw a photo of different positions in different positions, you have to move your brain.

Figure 4: Gray diagram of a buddy photo (left), the black and white two -value chart (middle) obtained by rough approximation, the black and white two -value chart (right) obtained by pixel optimization

Photo source: Light Popular Popularity Square/Veer

For example, if we want to show this gray photo of a buddy abroad, if the grayscale value of different pixels is similar to pure black or pure white, the light gray will be "four houses and five entry" white, and dark gray will always "four houses and five entry" as " Black, the final result is as horrible as the second picture. The entire "big flower face", and the third picture looks much more comfortable, it seems that the grayscale depth is variable, not only the two colors of all black and all white white , But if you take a closer look, there are still only these two pixels, but because of the use of an algorithm called "error diffusion" [1], which reasonably controls the black and white pixel ratio in different areas. In the dark area, the relatively dense area of ​​the white dot represents the area where the area is bright, and the accuracy of the color depth is exchanged for the color of the color, just like it has changed the magic, bringing a complete gray viewing experience.

And using a limited number of brushes to create a ever -changing color can also be done. In the color display, red and green and blue are three primary colors. Mixed red and green light can produce yellow light. Green and blue light mixed can produce blue light. Mixed red and blue light can produce purple light. Both the three primary colors are mixed together to obtain the results. It is white. Ideally, a pixel can produce three primary colors of red, green and blue (RGB) at the same time, and the intensity of the three channels can be freely adjusted, which can easily mix various colors. The ideal is beautiful, and the reality is skinny. If a pixel can only display red or blue separately, what should I do if I want to match the purple?

In the following chessboard grid patterns, each block is red or blue, and the number ratio is 1: 1. From left to right. As the grid gradually becomes smaller, it is equivalent to smaller and dense pixels. Red and blue disappear, and the entire pattern eventually became purple. This is actually wrong! All the pixels in all patterns (including the right) are only red and blue. Purple is an illusion caused by the human eye fusion of red and blue pixels, or the color that does not exist out of thin air. Figure 5: The size of the red and blue blocks gradually decreases and fused into purple

Picture source: Jiao Shuming

In the left picture below, each pixel has only 256 possible colors. When the color layer of the more abundant performance appears to be unpopular and stretched, and after the position of the pixel point is more reasonable, the picture on the right is obviously more increasingly even more increasing. Pleasing to the eye.

Figure 6: The original 256 -colored picture (left) The effect after optimization (right)

Photo source: Wikikylim sharing resources

We can obtain a new color of "ostomy" through the spatial distribution of limited number of color pixels, while the time dimension is another way. For a simple example, many people must have played such games when they were young. They made a small disc with a hard paper board. The small disc alternates red and yellow alternately, and then put a small pillar in the middle of the small disc Small discs are rotating as quickly as a gyro. What do you see? That's right, the small disc is neither red nor yellow, but the red and yellow two -colored "round class" flashed in front of your eyes and was "tuned into" orange in the middle. When the display is playing the video, it is actually equivalent to the static pictures of dozens of static pictures per second quickly, and the human eyes have the visual retention effect. Two primary colors can naturally deceive your eyes to see the new color after fusion.

In fact, the above -mentioned images have a special name: Dithering. This is to be mentioned from the Second World War decades ago. At that time, the electronic computer had not been invented. The American military bombers could only use mechanical computers when calculating the flight direction and the bombing curve. The gear and leverage parts, don't look at the accuracy of the calculation, it's quite delicate, afraid of touching the fall, and suddenly the bomber's cockpit is not as comfortable as sitting on the sofa at home. The parts shocked a few, so that the mechanical computer could not be played, the plane was lost, and the bomb was about to throw it on its own position. However, such a computer is quite aggressive, and it has not been swaying on the plane. It is unexpected that the results of the calculation are more accurate than when using it on the ground steadily, which is puzzled. Now that it has this "weird temper", engineers have once specially designed vibers that simulate the flight state, so that the mechanical computer can also experience the feeling of flying on the ground to enhance the accuracy of calculation.

Why do these guys use it better on the plane? It is mainly because the early mechanical parts are not like the current computer can accurately reach the decimal point. There are only many places after the decimal point. Only limited digits. Suppose can only be accurate to ten (100,110,120,130,140, ​​...). 120 said, and 128 can only be expressed in 130. This is obviously not reliable enough. After step -by -step calculations, the error will accumulate more and more. Rather than expressing 123 with 123 with "lack of two less" every time, a smarter way is that 123 is sometimes represented by 120, and sometimes it is expressed in 130, but because it is closer to 120, it is expressed in 120, and the accounted for 120 is expressed in 120. Slightly more, like a cup of hot boiling water and a cup of zero -degree ice water proportional proportion, which can blend out a hot and cold water in the middle. And shaking the mechanical computer is equivalent to introducing errors, just to make a part of the operation that can be failed normally every time, and the four are reluctant. The effect of "numerical blending". This is a wonderful idea of ​​"attacking poison" by adding some random small errors to resolve the calculation when calculating the calculation. This is the earliest source of the jitter technology [2].

In 1946 after the end of World War II, ENIAC, the world's first modern electronic digital computer, was born in the University of Pennsylvania. The mechanical computer gradually faded out of the historical stage, but the jitter technology shined on the stage of another color display technology. From the early stages of the development of various cameras and monitors, to this day, a tricky trouble encountered when it is faithfully recorded and reproduced the colorful real world. The performance of the TV computer display is particularly outstanding. Similar to solving the jitter method when the early computer represents the insufficient number of values, just like the painter uses the color panel, we can use a variety of existing colors to blend out of the non -existent color. After all, people's "eyes" are not so good, and they can combine small pixels with close positions or rapidly changing pixels at different times to perform virtual coloring. With the development of technology, the most common mobile phone display can also directly support many colors, often no longer need to create new colors, but many professional display devices used in the laboratory for specific scenes are limited. Relying on related technologies, such as the liquid crystal spatial light adjustment device and digital microscopy device for holographic three -dimensional display [3] [4] [5]. In terms of perception of color, there are many other incredible phenomena of human vision. For example, the picture below, do you impress it at first glance that it is a color photo?

Figure 7: color assimilation grid visual unclear picture

Picture source: stuarthumphryes (Twitter)

The truth is that most of the pixels in this picture are gray and cannot distinguish the color. Only the pixels covered in the gray photo of the gray photo are color. Of course, these pixels are not set at will, but compared to compared The corresponding color of the corresponding pixels in the photo is performed. It can be simply understood as the pixel color on the grid is much brighter than normal, and the saturation is very high. In comparison, the gray pixels of the background have no color at all. The saturation is 0. The two "extreme" pixels are under the fusion of the human eye, making the entire photo look normal. The above effect is called color assimilation grid vision [6]. Of course, we can also design the grid more densely to the scale of a single pixel. More difficult to be discovered.

Finally, let's go back to the red delicious cola can at the beginning of the article. This is another misjudgment of the color of the human eye. The strawberry pictures below also have similar effects. To produce such image effects, the specific method is: decompose the original normal color photos into a lot of tiny dots or fine lines. Taking lines as an example, two groups of interconnection. The red ingredients are set to 0, so the red part in these lines looks black or the part that does not have red looks blue, and the red ingredients remain unchanged in the other group. The value is maximum (overrive), and these lines will look white. Both of the staggered lines are equivalent to raising the intensity of green and blue, reducing the strength of the red, and watching the original photo through a filter that removes the red light. On a layer of blue veil. Due to this case, even if the original red object is actually black, in turn, for the other way, for the surface that looks like black objects, human eyes and brain instincts tend to restore them as red as red. So cola cana and strawberry are "dyed red", which is called the illusion of color constant sex [7].

Figure 8: Primitive color picture

Photo source: Light Popular Popularity Square/Veer

Figure 9: The illusion of red through two groups of staggered lines (zooming in the line on the right: Where is red?)

Photo source: Light Popular Popularity Square/Veer

Figure 10: Through two groups of cross -handed square grids to produce red illusion (the enlarged on the right is the grid: Where is the red?)

Photo source: Light Popular Popularity Square/Veer

The above "scams" are enough to prove that human vision has a weak ability to identify colors at some point, but a more outrageous example [8] is still below. Similarly, a dark gray and one white. But as long as you block the junction between the two with a finger, you will find that the color of the two objects turned out to be the same! This result will definitely make you crazy.

Figure 11: A picture that subverts your color shade judgment ability

Picture source: American scientist .org

After reading this article, do you still believe your eyes?

They do often make all kinds of inexplicable mistakes. Each error "changes it if it is committed, and the crime is changed", but it is also this kind of kindness deception that prompts you to "brain supplement" the color that does not exist in real objects. The world you perceive is more colorful.

The cover map of this article is provided by Light Popular Popularity

Reference materials:

[1] R.W. Floyd, L. Steinberg, An adaptive algorithm for spatial grey scale. Proceedings of the Society of Information Display 17, 75–77 (1976).[2] Ken C. Pohlmann (2005). Principles of Digital Audio. McGraw-Hill Professional.

[3] S. Jiao, D. Zhang, C. Zhang, Y. Gao, T. Lei, and X. Yuan, "Complex-amplitude holographic projection with a digital micromirror device (DMD) and error diffusion algorithm", IEEE Journal of selected topics in Quantum Electronics, 26 (5), 2800108 (2020)

[4] X. Yang, S. Jiao, Q. SONG, G.-B. MA, and W. Cai, "Phase-only color rainbow hophic near-ele display", Optics Letters 46 (21), 5445-5448 (2021)

[5] K. Liu, Z. He, and L. Cao, "Pattern-Adaptive Error Diffusion Algorithm for Improved Phase-only HOLOGRAM Generation," CHINESE Optics Letters 19 (5), 050501 (2021).

[6] S. Jiao and J. FENG, "Image Steganography with Visual Illusion," Opt. Express 29 (10), 14282-14292 (2021)

[7] https://www.wired.com/story/remember-dress-heres-why-we-all-see-colors-differently/

[8] Purves D, Lotto RB, Nundy S. Why we see what we do: A probabilistic strategy based on past experience explains the remarkable difference between what we see and physical reality. American Scientist. 2002 May 1;90(3): 236-43.

Reprinted and released by authorized this article

Writing | Jiao Shuming, Assistant Researcher at Pengcheng Lab, Ph.D. in Electronic Engineering, Hong Kong University

Review expert | Cao Liangcai (Tsinghua University)

WeChat editor | What is cool

- END -