Trucos de diseño para diseñar como locos

What’s in an image

What is an image document? What is the difference between size and print resolution? Although for most graphic designers this may seem a trivial question, there are many professionals who are initiated into the world of design without this knowledge. I myself, for example, come from another profession and started my life as a designer in 3D, creating my first textures with PhotoShop unaware of the darker significance that lay behind those terms.

As has happened at other times Wikipedia will provide some links for all those wishing to see a more detailed explanation about the terminology.

A document image is a data file created specifically to store an image, either a bitmap or vector objects. There are different standards for data format, such as: JPEG, TIFF, BMP, EPS, etc…

There are image formats that store the image with great accuracy: PNG, RAW, TIFF, BMP, etc…, while others are used to compress the images so that they occupy less space: JPEG, GIF

Many image formats support various configuration options, such as types and levels of compression. Also, some of them offer interlaced. There are dozens of image formats, most of them created by large companies.

The information within a digital image document is organized as follows: header, metadata and image data itself.

The main confusion among many designers is the relatives between image resolution and printing resolution. There is a difference between the two.

The amount of information concerning the image contained in the document is measured in pixels (width x height) and is called resolution, or to be more concise image resolution. Therefore, whenever talking about image quality refers to the resolution measured in pixels. In the picture below you can see a sample of how the resolution works. From left to right starting with an image of 3 x 3 pixels to finish in a 90 x 90 pixels. Each pixel can only assume a combination of color, for that reason the image on the left shows no sign of identity, the only thing that can represent at that resolution is a small colored dot. As resolution increases, right, is easier to go to form a definite image.

The print resolution is measured in dpi or dots per inch (1 inch = 2.54 centimeters) and details the number of dots a printer can print in an inch of paper.

The relatives between image resolution and printing resolution are easy to understand now. The picture below shows an image with a resolution of 3.504 x 2.336 pixels set to 72 dpi (right) and 300 dpi (left). To view more detail the measures listed just click on it.

The extent of the image in centimeters (width by height) is different, at 72 dpi image has a scale of 123.61 x 82.41 cm. Set to 300 dpi measures just 29.67 x 19.78 cm. Image resolution had not changed, in example changing the print resolution had not redraw the image and, therefore, its measurement in pixels had not changed, nor had the weight of the document, 31.2 MB.

The image below shows a comparison of the same image at 300 dpi and 72 dpi, left and right respectively. The difference to the example above is the image on the right was redrawn to have the same size in centimeters that the image on the right.

Now the image resolution of the document image to the left is 841 x 561 pixels. The image quality has decreased, the size of the document has come down to 1.80 MB. This process is necessary when it comes to preparing high-quality images for publication on the Internet.

Sometimes it is necessary to enlarge the image size by increasing its resolution in pixels. Whether by approximation or other mathematical algorithms the result depends very much on the quality of the original image, and the increase that has to be achieved.


Links: Wikipedia


About mimoriarty

Diseñador gráfico multidisciplinar; me gustaría trabajar y compartir experiencias con diseñadores de todo el mundo

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This entry was posted on April 10, 2010 by in Conocimientos, multilanguaje and tagged , , .

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