A design file my designer sent shows up with negative-looking colors inside the PDF; what is going on?
Most likely the image is saved in CMYK, the color mode used for printing. The tool embeds JPEG files exactly as they are, and some PDF readers display this kind of CMYK image with inverted colors. Ask your designer for an RGB export, or re-save the image as RGB, then build the PDF again.
CMYK and RGB in plain words
Screens make colors from red, green and blue light: that is RGB. Printing presses make them from four inks, cyan, magenta, yellow and black: that is CMYK. A designer preparing work for a print shop usually exports images in CMYK, which is exactly right for the press, but can cause trouble when the same image is used anywhere else.
Some design software writes CMYK JPEGs with the ink values flipped, plus a marker inside the file saying so. Programs that honour the marker show the image correctly; those that do not show it inverted, with white turned dark and red turned greenish, like a negative.
Why the tool does not fix it automatically
Images to PDF embeds JPEG files byte for byte, with no decoding or re-encoding, which is what keeps their full quality. The trade off is that it does not change the color mode: the image goes in as CMYK, and how it looks depends on the reader that opens the file. So it can look fine on your machine and inverted on your client's, or the other way round. And if a JPEG uses an encoding the PDF library cannot read at all, the tool refuses it and names the file rather than producing a broken PDF.
How to fix it
- Ask the designer for a screen version: a JPEG or PNG export in RGB, ideally sRGB. It is a common request and quick for them.
- If the designer is not around, convert the image with the Image format converter to JPEG or PNG. That redraws it in the browser in screen colors. Open the result and check the colors before using it, because the browser itself may not read a CMYK file perfectly.
- Add the new image to the converter and build the PDF again.
- Open the file in more than one reader, such as your phone browser and a desktop viewer, before sending it to the client.
How to spot a CMYK image in advance
- It came from a designer as part of print ready files or alongside a print shop PDF.
- The file is larger than usual for its dimensions, because it carries four color channels instead of three.
- It looks dull or odd in some apps and fine in others.
If the goal is professional printing at a print shop, design files are better kept away from this tool altogether. Ask the designer to export a print PDF straight from the design software, which knows the press settings. This tool is for gathering screenshots, documents and catalogs, not for preparing press files.
Common questions
Does this happen with phone photos?
Rarely. Phone cameras save in RGB; the problem almost always comes from design software files.
What about PNG images?
PNG does not support CMYK, so this issue is specific to JPEG files.
The tool refused one image and named it; why?
The PDF library could not read its encoding. Re-save it as an ordinary RGB JPEG and add it again.