Image Formats: what and why?
Whether you want to print your photos, insert graphics into a text file, post a picture on the internet there is adequate and suitable for every occasion format: Jpeg, Tiff, Png, Gif. In this article we explain the differences between each
Each format has its own characteristics . To properly choose the one that corresponds to what you want to do with any image is essential to meet the specific needs of each characteristics.
Expressed in bits, the color depth is the total of color values that can take each pixel of image. JPEG , for example, uses a color depth of 24 bits (ie, 8 bits for each primary color : red, green , blue) , corresponding to more than 16.7 million hues for a pixel . Since the human eye is unable to discern many shades , and since most printers can not return them , this amount is more than enough.
However, photo cameras and high-end scanners capture images with a color depth of 12, 14, and 16 bits per primary color , that is, several million colors. This allows more information to register , useful when retouching the image, preserving the small details and apply correction filters more accurately. It also provides a larger margin of maneuver before finishing with a visible image degradation .
Lossless compression , TIFF possible and PNG for example, reduces the weight of some images without altering its quality. By contrast, the standard JPEG compression format is , we might say , destructive : eliminates image information . Although the compression is effective, it is also risky : more the higher the image quality is degraded .
The pixel is the smallest and most significant element of a digital image . Each pixel is colored , decomposed into red, green and blue . The juxtaposition of the pixels, like a mosaic , creates an image. The pixel is used as the unit of measure of the size of display screens . A pixel is not necessarily square. Its shape depends on the display stand and the technology used .
Joint Photographic Expert Group. Very expanded format , JPEG became a standard for both photography and images for publication on the Internet ( all browsers accept without problems) . Defined in 1992, is a lossy compression format : reduces the weight of an image by removing ( irreversibly ) redundant information.
Each imaging software defines its own scale compression for example from 1 to 99 or 0 to 12 - the weakest figure corresponds to the higher compression. In this case, the weight of the file can be divided into 50, but the image is highly degraded . Please note that whenever you keep a JPEG compression brings a new and , therefore, further degradation . Therefore it is recommended to save an image in JPEG only after making all the adjustments, and then not manipulate .
Number of colors : 16.7 million
Number of gray shades : 256
Management transparency : no
Use: photographs and illustrations, web publishing , printing
This variant of the JPEG format , serviced in 2000 by the Joint Photographic Expert Group, is rarely used outside of professional media work. More and more softwares accept , but without proposing all compression options. Few web browsers are able to work with this format , unless a specific extension to do is add . As for cameras photographs , most ignore it. The 2000 lets you choose JPEG compression lossy or lossless compression of data. Your lossy compression is much better than the classic JPEG: JPEG 2000 produces less degraded images . Visually, the difference becomes obvious only when too compressed image .
Compression with or without loss of data ( user selectable )
Number of colors : 16.7 or 32 million
Management transparency : no
Use: photographs and illustrations, print
Graphics Interchange Format . Developed in 1987 by CompuServe, this lossless compression format is adapted primarily to the images to the Web . It is capable of fixing 16.7 million shades, but you can only register 256 at the same time in an image. Gif format is not at all suitable for photography. It is very effective , however , for images with few shades of color ( logos, graphics ) . Gif also manage the effects of transparency and enables animated images. That's why , despite the emergence of competing formats (such as PNG) , Gif still has some success in Internet emoticons for MSN , for example.
Number of colors : 256
Management transparencies : yes
Use: Web publishing (except for photography ) , animated images
T agged Image File Format . Perfected in 1987 by the company Aldus , then obtained by Adobe , this format does not evolve since 1992. It is used , depending on the choice of uncompressed manner with lossless or lossy , but mostly in the middle of editing. Tiff preserves images in a very high quality images and allows you to work in layers ( the software like PhotoShop retouching images work by layers: each layer is like a transparent sheet on which modifications are made and that certain elements are placed amend the original image ; layers allow a true work of differentiated and easier assembly ) . In its compressed version , lets you choose between numerous compression systems (ZIP , LZW ) , including JPEG . Production of heavy files is intended primarily for professional use and preparing images for printing, and excludes any use for a Web publication.
Compression with or without data loss
Number of colors : 16.7 million to several million
Management transparency : no
conservation layers : yes
Use: photographs and illustrations, print
Portable Network Graphics. PNG was developed by the W3C (World Wide Web Consortium ) , the promoter of Web standards , which makes it to be accepted by all browsers. Has the ambition to replace GIF and JPEG in the network. It is a lossless compression format of information, capable of restoring 256 to several million colors. Very effective for compressing graphic images with flat bottoms , that is much less optimal JPEG photos if it comes . As Gif, manage transparency , allowing , for example, set graphics objects drawn into websites, keeping the theme page background .
PNG , however , does not accept animated images. A format derivative, MNG (Multiple- image Network Graphics) was developed for this function , but most browsers do not accept it , which makes their use is very rare.
Compression: Lossless
Number of colors : 256 to several million
Management transparencies : yes
Conservation of layers : no
Use: Web publishing (except for pictures )
JPEG , TIFF , PNG
Each format has its own characteristics . To properly choose the one that corresponds to what you want to do with any image is essential to meet the specific needs of each characteristics.
A first feature: the depth of the colors.
Expressed in bits, the color depth is the total of color values that can take each pixel of image. JPEG , for example, uses a color depth of 24 bits (ie, 8 bits for each primary color : red, green , blue) , corresponding to more than 16.7 million hues for a pixel . Since the human eye is unable to discern many shades , and since most printers can not return them , this amount is more than enough.
Question of details
However, photo cameras and high-end scanners capture images with a color depth of 12, 14, and 16 bits per primary color , that is, several million colors. This allows more information to register , useful when retouching the image, preserving the small details and apply correction filters more accurately. It also provides a larger margin of maneuver before finishing with a visible image degradation .
Another important criterion compression.
Lossless compression , TIFF possible and PNG for example, reduces the weight of some images without altering its quality. By contrast, the standard JPEG compression format is , we might say , destructive : eliminates image information . Although the compression is effective, it is also risky : more the higher the image quality is degraded .
Pixel, what does it mean ?
The pixel is the smallest and most significant element of a digital image . Each pixel is colored , decomposed into red, green and blue . The juxtaposition of the pixels, like a mosaic , creates an image. The pixel is used as the unit of measure of the size of display screens . A pixel is not necessarily square. Its shape depends on the display stand and the technology used .
JPEG: the universal format
Joint Photographic Expert Group. Very expanded format , JPEG became a standard for both photography and images for publication on the Internet ( all browsers accept without problems) . Defined in 1992, is a lossy compression format : reduces the weight of an image by removing ( irreversibly ) redundant information.
Each imaging software defines its own scale compression for example from 1 to 99 or 0 to 12 - the weakest figure corresponds to the higher compression. In this case, the weight of the file can be divided into 50, but the image is highly degraded . Please note that whenever you keep a JPEG compression brings a new and , therefore, further degradation . Therefore it is recommended to save an image in JPEG only after making all the adjustments, and then not manipulate .
JPEG
Compression : lossyNumber of colors : 16.7 million
Number of gray shades : 256
Management transparency : no
Use: photographs and illustrations, web publishing , printing
JPEG 2000 : little known
This variant of the JPEG format , serviced in 2000 by the Joint Photographic Expert Group, is rarely used outside of professional media work. More and more softwares accept , but without proposing all compression options. Few web browsers are able to work with this format , unless a specific extension to do is add . As for cameras photographs , most ignore it. The 2000 lets you choose JPEG compression lossy or lossless compression of data. Your lossy compression is much better than the classic JPEG: JPEG 2000 produces less degraded images . Visually, the difference becomes obvious only when too compressed image .
JPEG 2000
Compression with or without loss of data ( user selectable )Number of colors : 16.7 or 32 million
Management transparency : no
Use: photographs and illustrations, print
GIF : Animated images for
Graphics Interchange Format . Developed in 1987 by CompuServe, this lossless compression format is adapted primarily to the images to the Web . It is capable of fixing 16.7 million shades, but you can only register 256 at the same time in an image. Gif format is not at all suitable for photography. It is very effective , however , for images with few shades of color ( logos, graphics ) . Gif also manage the effects of transparency and enables animated images. That's why , despite the emergence of competing formats (such as PNG) , Gif still has some success in Internet emoticons for MSN , for example.
GIF
Compression: LosslessNumber of colors : 256
Management transparencies : yes
Use: Web publishing (except for photography ) , animated images
TIFF for print
T agged Image File Format . Perfected in 1987 by the company Aldus , then obtained by Adobe , this format does not evolve since 1992. It is used , depending on the choice of uncompressed manner with lossless or lossy , but mostly in the middle of editing. Tiff preserves images in a very high quality images and allows you to work in layers ( the software like PhotoShop retouching images work by layers: each layer is like a transparent sheet on which modifications are made and that certain elements are placed amend the original image ; layers allow a true work of differentiated and easier assembly ) . In its compressed version , lets you choose between numerous compression systems (ZIP , LZW ) , including JPEG . Production of heavy files is intended primarily for professional use and preparing images for printing, and excludes any use for a Web publication.
Tiff
Compression with or without data lossNumber of colors : 16.7 million to several million
Management transparency : no
conservation layers : yes
Use: photographs and illustrations, print
PNG: the standard format of the Web
Portable Network Graphics. PNG was developed by the W3C (World Wide Web Consortium ) , the promoter of Web standards , which makes it to be accepted by all browsers. Has the ambition to replace GIF and JPEG in the network. It is a lossless compression format of information, capable of restoring 256 to several million colors. Very effective for compressing graphic images with flat bottoms , that is much less optimal JPEG photos if it comes . As Gif, manage transparency , allowing , for example, set graphics objects drawn into websites, keeping the theme page background .
PNG , however , does not accept animated images. A format derivative, MNG (Multiple- image Network Graphics) was developed for this function , but most browsers do not accept it , which makes their use is very rare.
PNG
Compression: LosslessNumber of colors : 256 to several million
Management transparencies : yes
Conservation of layers : no
Use: Web publishing (except for pictures )
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