How to select the image format in the face

Source: Internet
Author: User
Tags scale image
The GIF format is used in the graphic area, which is too distorted. How can this problem be solved? This problem is simpler than just using JPG. We usually use three types of animated images: GIF, JPG, and PNG. So how can we choose to use these three formats? Here are some of my views on the use of these three formats.

Next, let's first understand the official solution of the comparison between different formats (refer to the following content from Baidu ):

GIF indicates Graphics Interchange format (Animated cross-border format). The Animated GIF is named gif. Currently, all the animated images support the GIF format, and some animated images only recognize the GIF format. GIF is an index coloring format. When there are few colors, the generated file size is small, and its highlights are as follows:

1. The GIF format supports transparent background. If the background color is set to transparent, a GIF image is combined with the background of the receiver to generate a non-rectangular image.
2. animated GIF formats are supported. Before the Flash drive appears, GIF animation can be said to be the only dynamic form in the webpage. In GIF format, you can combine images in a single screenshot, and then play each screenshot as an animated GIF. Although not all animated GIF images support GIF animation, the latest animated GIF animation supports GIF animation.
3. The GIF format can be simplified. A video clip is displayed on the screen. A video clip is faster than a non-video clip, this allows the publisher to know the overview of the photo.
4. The GIF format supports no supported animated images. The "no-picture" method is an effective method for generating images without missing images. The reason is that the GIF format uses the "no-picture" method, therefore, it is more suitable for condition, criterion, and condition.

The missing points in GIF format are exactly the same. Index coloring is a product left by historical users. In DOS, the old users almost have no exception in indexing coloring, this format should have been eliminated for a long time. However, due to the bandwidth restrictions, GIF is transferred from the DOS time to the Internet time. The biggest disadvantage of the GIF index coloring format is that it has only 256 colors, which is not suitable for the photo quality.

JPEG stands for Joint Photograhic Experts Group (Joint photo Photo photo family). This format is often converted into JPG, And the JPG picture is named jpg.

The most important aspect of JPG is that it supports hundreds of colors and can be used to present photos. In addition, because JPG images use a more effective algorithm, the file length is reduced and the next upload time is shorter. When there are some images, some images in the images will be stored to reduce the file length. Its memory usage ratio is relatively high. The memory usage ratio is 180: 1, in addition, the quality of Images cannot be too large from the perspective of images, which greatly facilitates the transfer of online images and magnetic images. JPG animated GIF is more suitable for photos, because missing images are not as explicit as those provided in the photo. In addition, JPG has a larger proportion of images, and the final quality is also better.

However, from the perspective of growth, JPG should also be a phased-out video format because of its continuous improvement and Memory enhancement, this is because of the loss of images that cannot be recovered. Therefore, JPG images that have been uploaded are generally not printed in combination. It is best not to use JPG when preparing important images. Also, JPG is not as lively as GIF images. It does not support animated images and transparent backgrounds, but does not support animated images.

PNG is the image file storage format that was developed in October 1990s. It aims to replace the GIF and TIFF file formats, some GIF file formats are not supported at the same time. The Portable Network Graphic Format (PNG) is derived from the unofficial "PNG's Not GIF". It is a bitmap file) save the token format, and convert it to "ping 」. When PNG is used to save a gray-scale image, the depth of the gray-scale image can be up to 16 bits. When the color-scale image is saved, the depth of the color-scale image can be up to 48 bits, and the number of Alpha channels with up to 16 bits can be stored. PNG uses the non-linear regression algorithm derived from LZ77.

The PNG file format retains the following features of the GIF file format:

● You can use a color lookup table or a color palette to support 256 colors of colored images.
● Streamability performance (streamability): The image file format allows both outgoing and incoming image data.
● This feature is suitable for generating and displaying images during communication.
● Progressive display, after the whole picture is displayed, the image will be displayed gradually, that is, the image will be displayed with a low resolution, and then its resolution will be gradually increased.
● Transparency: This performance allows some parts of the photo to be invisible and used to build some distinctive images.
● Assistant information (ancillary information): This feature can be used to store some textual information in the photo file.
● Establish the hardware environment on the computer.
● Use non-linear regression.

Add the following features not available in the GIF file format:

● Each pixel is a 48-bit real-color photo.
● Each pixel is a 16-bit grayscale pixel.
● The α channel can be added for the gray-scale and true-color colors.
● Add the Gamma information of the photo.
● Use cyclic redundancy (cyclic redundancy code, CRC) to distribute malicious files.
● Accelerate the method for displaying the portrait images in a successive approach.
● Standard release/release toolkit.
● Multiple images can be stored in one file.
● File structure

The three formats have their own weaknesses, among which there are many PNG nodes. Although it is still quite common, the increasing popularity of its special features has made us very interesting about its production. At least I like this format very much now. Of course, for example, the overall workload of the graphic operator is the stress. Therefore, we still need to pay attention to the mixed use of these three formats. So when will the GIF be used? When will the PNG be used? Let's analyze them one by one.

In my real work, I found general colors, such as some small standards and even background, with less colors, therefore, the GIF format has only 256 colors, but it must be very compatible with such images. Of course, we do not rule out the richness of some special small standards, however, I believe that the color of the image is a little lost and will not affect the overall effect of the image. Therefore, the animated GIF image is as follows: small-sized porn clips with less colors, such as the logo and background.

So how can we choose a large image? First, let's first understand JPG. All our friends who use Photoshop know that, there will be a place for us to choose the quality of this JPG clip when we finally release the video. 100% indicates that the image is not damaged, when we use the same video to produce different quality tablets, we find that the products with low quality are much better than those with high quality, in this way, the photo looks very bad. Of course, we also found this kind of picture highlighted in the large-colored pictures. Such as the sky and portraits. Especially when the face is shown as black spots. Of course, JPG can be used and the quality is reduced if the photo quality requirement is not limited. However, it is not applicable to background or small standards.

I personally think that PNG is a choice between GIF and high-quality JPG, PNG is much larger than GIF, but it is similar in quality. If it is a normal video clip, the PNG is still a little smaller than the JPG of high quality, but the PNG is still a little bit of color loss. However, if the film is not enlarged, it cannot be seen. We basically didn't aim to make people more nervous. Therefore, PNG is a medium choice. Of course, PNG also has a very large aspect, that is, transparency. Although IE6 did not support this feature before. GIF images are also transparent. However, GIF images only support transparent images, but do not support translucent images. Therefore, the animated images of GIF images usually have a circle of white dots. While PNG does not have such issues. When the development of the time generation shows that IE6 has become history, we can see the real power of PNG.

Of course, there is a special situation that may be quite special, that is, the matching between the background film and the foreground film, in this case, the color structure must be consistent to produce a sound effect. At this time, be sure not to use different formats in combination.

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