Tool Icon

Convert to Grayscale

Convert the elements of a document (annotations, form fields, graphics, images, text) to grayscale and save as PDF

Drop your file here or
Upload from your device
Upload from Google Drive
Upload from DropBox
Upload from Web address (URL)
Max file size: 256 MB

Your files are safe !

We use the best encryption methods to protect your data.

All documents are automatically deleted from our servers after 30 minutes.

If you prefer, you can delete your file manually right after processing by clicking the bin icon.

How to convert a document in grayscale online :

  1. To start, drop your PDF file or upload it from your device or your cloud storage service.
  2. Choose the document elements to convert to grayscale (graphic elements, images, text, form fields, annotations) and click the Convert to grayscale button.
  3. Download the PDF file to your computer or save it directly to your cloud storage service.

Did you know?

Grayscale is made of shades of light
Grayscale images are composed of shades from black to white. The information contained relates to luminance, not color. Luminance describes the amount of light emitted from, passed through, or reflected off an object. On the contrary to brightness, which is subjective (visual perceptions and physiological sensations of light can be different among individuals), we can measure luminance.
Grayscale, also known as achromatic (from Ancient Greek “no/without color”), happens when, for instance, we remove the color information from a standard image. A truly black and white image only contains pure black and pure white. Grayscale images are black, white, and everything in between.
Luminance and brightness are more important than the color information in an image. Why? If we remove the color information, the image is still visible. However, if we delete the luminance information, the result is an entirely black image with nothing left to see!
Converting color PDFs to grayscale makes them lighter
Color images are bigger (size-wise) than black and white and grayscale images. You compress the PDF to a smaller size by converting it to grayscale. It will work even better if it contains many images.
In addition to making PDF lighter, you will save ink if you need to print it.
Surprisingly, if you’re using a printer with color cartridges, setting the printing parameters to grayscale instead of black and white will also save your black ink cartridge. This is because the shades of grey actually use a very small amount of colored inks instead of only black ink.
Coming back to PDF, a black and white file will always be lighter than a grayscale one, but it may not correctly render finer details and transparency. If you wish to make your PDF file as light as possible without compromising the quality of the images and illustrations, take a look at our Hyper-compress tool that uses MRC technology.
There are many different methods to convert color to grayscale
The average method is the simplest because it takes the colors' average. For example, for an RGB image (which includes the three primary colors red, green, and blue), the formula is grayscale = (red + green + blue / 3). However, this method doesn't consider the wavelength of the different colors, so the converted image will appear darker than it should be.
Another option is the luminosity or weighted method, based on
colorimetry . Its goal is to measure how much each color contributes to an image by calculating its wavelength (red has more wavelengths of all three colors). This method gives better results because it also considers human perception. Studies show that the human eye perceives colors differently. For instance, green is easier for the eye than red.
Many other algorithms (lightness method, desaturation, and more) exist, each adapted to a specific type of image.