The pictures uploaded by WeChat official account are not clear, so this useful method must be remembered!

The compression algorithm of wechat has been changing. The clarity and saturation of an image are related to too many factors. Images uploaded by different mobile phone models (with different mobile phone resolutions) will be slightly different. Wechat compresses pictures to improve loading speed and reduce the pressure on the server.

Wechat WeChat official account uploads pictures in the background. The pictures we upload cannot be perfectly adapted to different types of mobile phones, nor can we completely avoid the compression principle of WeChat. I don't know the compression algorithm of WeChat. What can I do to maintain the image quality effectively to the greatest extent?

If you can use png, use png.

The original size and width of the still picture are kept at 1080 px to avoid being compressed.

There are other suggestions and principles, continue to look down.

Image format: bmp, png, jpeg, jpg, gif format.

Picture size: Any single picture must be less than 5M, in which gif is less than 2M.

Uploading pictures from the local area to the official WeChat account background will be compressed. Previously, WeChat official picture rules suggested that,

This statement is no longer valid at present, and the picture will not be automatically compressed to 640 pixels. This can be verified by yourself.

In fact, when viewing the images of WeChat official account on PC and mobile phone, if the resolution of all the images exceeds the resolution of the reading area, for example, the images larger than the screen resolution of the mobile phone, all the images will be displayed in the same size, even if the pixels of the original images are different.

So along this line of thought, can we achieve the best compression effect by adjusting the resolution or changing the format of the picture?

We analyzed the commonly used jpg, png, gif images, and after repeated tests, we finally found the law of WeChat background image compression. You can view the elements in the PC browser.

Because the pictures will be compressed again, the color difference of many pictures can't be distinguished by the naked eye, but the contrast can still see the obvious difference clarity. According to the conclusion of the following test, experiment on your own according to the specific situation!

Jpg image compression:

Jpg width pixel ≤ 1080, the picture is not compressed.

The Jpg width is pixels > 1080, and the image is compressed to 1080.

Png image compression:

Png and jpg image compression are the same.

Png width pixel ≤ 1080, the picture is not compressed.

Png width pixel > 1080, and image compression is 1080.

Gif image compression:

Gif frame number > 60, the picture is not compressed.

When the number of gif frames is less than or equal to 60,

Picture width pixel > 640, picture compression is 640.

Picture width pixel ≤ 640, the picture is not compressed.

The number of Gif frames = 1 frame, and the gif picture of 1 frame is equivalent to the output of still images in gif format.

Width pixel ≤ 1080, the picture is not compressed.

Width pixel > 1080, and image compression is 1080.

According to the above picture resolution results, it is found that in the range of less than or equal to 1080px, the larger the picture size, the clearer the picture, while the picture with a width greater than 1080 px is easy to be compressed, so we try to output the picture with a width of 1080 px when inserting the picture, and the pictures with different formats are suitable for different picture scenes.

Picture size:

Png & gtgif & gtJpg (under normal circumstances)

Image transparency effect:

Png & gtgif & gtJpg (not supported)

Color richness:

jpg & gtpng(png-24 & gt； Png-8) > exchangeable image format

Picture clarity:

Png & gtgif & gt uses jpeg file exchange format to store the file extension of the encoded image.

We can also do experiments, choose pictures of the same size and output them in different formats to see which effect is better.

Through comparison, it is found that the differences between each group of pictures are not obvious, and only subtle differences can be seen by the naked eye.

Among them, jpg pictures have the highest compression degree, the best quality and simple color, and png pictures are output in png-8 format, color photos and color design drawings, and png-24 format.

How to change the image format: open photoshop→ click the file in the upper left corner → export button to select all formats and save them as Web → finally click Save.

Sample screenshot:

If you look at the red part carefully, jpg images are the most blurred, while png and gif images are relatively better preserved.

Illustration:

Only when you zoom in on the same picture on your mobile phone can you find different compression conditions.

Png pictures are the smoothest and the best in quality, followed by jpg pictures, and gif pictures have the worst noise quality. The viewing effect on the mobile phone is more obvious than that after Zhihu uploaded it.

What is the principle of this situation?

Gif: Lossless compression is adopted. Compared with uncompressed bmp format, it is smaller and supports transparency and animation. However, gif can only express 256 colors at most, so pictures with complex colors and rich details are not suitable for saving in gif format. Logo, icon and wireframe with simple colors are all suitable for gif format.

Jpg: Lossy compression, supporting colors above 1600W (2 24). When you copy and save the edited picture repeatedly, the picture quality will decrease. Jpg is very suitable for colorful and gradual pictures, but not for icons and logo. Compared with gif and png-8, jpg file size has no advantage.

Png: Using lossless compression, compared with gif, it supports transparency better (png supports defining 256 transparency levels for the original image, so that the edge of the image can be smoothly blended with any background) and its size is smaller. If you need to express higher quality colors and rich details, you need to export png-24, but png-24 is larger than png-8 and does not support animation. On the premise of ensuring clear and realistic pictures, png format pictures are preferred.

Png-8 refers to 8 bits, which is equivalent to using 2 8 (the eighth power of 2) to store the color type of the picture, which means that png-8 can store 256 colors. If a picture has fewer color types, it is more appropriate to save it in png-8 format.

Png-24 refers to three 8-bits, which respectively represent RGB values. That is to say, png-24 can express 256 * 256 * 256 (1677 7216) colors, so png-24 expresses more colors than png -8 and takes up more space than jpg.

At present, it has not been said that WeChat will not compress gif images.

* Still pictures:

Wechat is more friendly to png pictures. When the image compression is unclear, we can export the png-24 image with the width of 1080 px.

* animation:

If the number of frames is greater than 60, the maximum width of the moving picture shall not exceed 1080 px.

The number of frames is less than or equal to 60, and the maximum width of the moving picture does not exceed 640 px.

Of course, it does not rule out that the picture in gif format works best when it is finally uploaded. After all, there are too many factors that affect the quality of image compression. In short, I mainly output png, and I have tried to output pictures in different formats many times, and found the most ideal effect.

The picture is too big to upload, you can use phtoshop to reduce the size of the picture, or in? TingPNG？ Compress the pictures on the website.