How to Check If an Image Is Print-Ready for DTF Printing

1. What this document covers

Many print problems come from the image itself, not from the printer, the RIP software, or the settings. White edges, grey edges, rough edges, jagged edges, blurred edges, and color shifts are common examples. The printer outputs the pixels in the image as they are. Whatever is in the image appears in the printed result.

Use this document to confirm that an image meets the print requirements, before you import it into the RIP software. Checking costs far less than scrapping and reprinting, so run these checks every time.

1.1 The check flow

Open the image  →  run each check  →  compare against the quick reference table

All checks pass  →  chapter 4, export the PNG  →  import into the RIP software and print

A check fails  →  go to the section or document named in the table  →  return to chapter 3 and check again

1.2 The 7 checks (quick reference table)

The table below covers everything in this document. Use it to judge the image first, then open the section named for the detailed steps.

Note: Editing cannot repair a quality problem in the image. If the original is blurred, low in pixels, or has been compressed repeatedly, no process recovers the lost detail. Replace the original instead.

2. Image requirements

2.1 Image sharpness

Use a sharp original image. The following are not suitable for printing directly:

• The image is blurred, out of focus, or lacks detail
• The image has too few pixels, and shows blocks when enlarged
• Screenshots, images sent through chat apps, and small images downloaded from the internet
• The image already shows blur, jagged edges, or clear distortion when enlarged

If the quality of the image is poor, get a higher-quality original. Do not try to edit a poor original and print it.

2.1-A-sharp-image-compared-with-a-blurred-image

2.2 Resolution and print size

A resolution value on its own means nothing. It has to be read together with the print size. The same image can be sharp at a small size and too coarse when enlarged. The requirement is: 300 PPI at the target print size.

Note: Image resolution is expressed in PPI (pixels per inch). Printer output resolution is expressed in DPI (dots per inch). The two are different measures. In everyday use, image resolution is often called “300 DPI”, which means 300 PPI.

Formula: suggested print size in cm = pixels ÷ 300 × 2.54

Read the print size directly in Photoshop

If you prefer not to calculate, let Photoshop show the size:

1. Click Image → Image Size.
2. Clear the Resample checkbox.
3. Set Resolution to 300, with the unit set to Pixels/Inch.
4. The Width / Height values now show the suggested maximum print size at 300 PPI.

Note: With Resample cleared, Photoshop only recalculates the displayed size. It adds no pixels and removes none. This is a view-only step and does not change the image.

Important: Raising the resolution value of a low-pixel image does not make it sharper. DPI is only the ratio between pixels and physical size. Sharpness comes from the total number of pixels. An image forced to a higher value prints visibly soft.

2.2-1-Click-Image-Image-Size

2.2-2-Uncheck-Resample-and-Set-Resolution-to-300-DPI

2.2-3-Read-the-Resolution-value

2.3 File format

2.3-1-PNG-PSD-JPG-and-Tiff-compared

2.4 Color mode (RGB / CMYK)

An RGB image can be printed directly. No conversion is needed for printing.

RGB and CMYK do print differently, but neither is better in every case. LINKO does not recommend one color mode over the other. Judge by the printed result and by your own preference.

To check the current color mode: click Image → Mode. The item that is ticked is the current color mode.

Is the printed result already stable, and you want to try a different appearance? Keep the original file. Convert a copy to CMYK for a comparison sample. Click Image → Mode → CMYK Color. To keep CMYK, save as TIFF, PSD, or PDF. Then print the comparison sample.

2.4-1-Check-the-Current-Color-Mode

2.4-2-Convert-to-CMYK-Mode

Important: PNG is not used to keep CMYK. If you export PNG after converting to CMYK, the file returns to RGB and the conversion has no effect. To keep CMYK, save as TIFF, PSD, or PDF.

Note: Converting RGB to CMYK cannot be undone. Keep a copy of the original RGB file before converting. Do not overwrite it.

2.5 Background

The image needs a transparent background. A white, black, or colored background is treated as part of the design and is printed with it.

Important: In Photoshop, only the grey-and-white checkerboard marks a transparent area. A white background is not a transparent background. The two look the same on screen, but a white background prints in full.

If the image has a background that is not transparent, remove it using Clean Image Edges chapter 3, then return here.

2.5-White-background-left-and-transparent-background-right

3. Check the image

After the requirements in chapter 2 are confirmed, enlarge the image and check the edges.

3.1 Open the image

1. Open Adobe Photoshop.
2. Click File → Open.
3. Select the image you want to print and open it.

3.1-1-Click-File-Open

3.1-2-Select-the-image-and-click-Open

3.2 Enlarge and check the edges

1. Hold Alt and scroll the mouse wheel to enlarge the image. Enlarge until the edge pixels are clearly visible.
2. Hold the space bar to drag the canvas. Follow the whole outline of the design, on all sides.

Look for the following:

• Background not fully removed, or leftover background color
• White edges or grey edges
• Unwanted semi-transparent edges
• Rough or clearly jagged edges

3.2-1-Enlarge-and-check-the-image-edges

How to add a contrast background

On a transparent checkerboard or a white canvas, white and light leftovers at the edge are almost invisible. Add a contrast background to find them.

1. Click Create New Fill or Adjustment Layer at the bottom of the Layers panel, then select Solid Color.
2. Select a color that contrasts strongly with the design, then click OK.
3. In the Layers panel, drag the solid color layer below the image layer.
4. Check once with a dark color and once with a light color. A dark background reveals white edges and light leftovers. A light background reveals dark leftovers and unwanted edges.

Important: The solid color layer is a checking tool only. It is not part of the image. Delete it or hide it before you export in chapter 4. If you do not, the transparent background is filled with that color and the whole area prints as a solid block.

3.2-2-Checking-edges-on-a-light-and-a-dark-background

3.3 Result

Confirm each item against the quick reference table in section 1.2:

• All 7 checks pass— continue to chapter 4 and export the PNG for printing.
• Any check fails— go to the section named in the last column of the table. After the image is corrected, return to section 3.2 and check again before exporting.

4. Export the image

After the image meets the print requirements, export the PNG for printing.

4.1 Before exporting

Important: Delete or hide the solid color layer created in section 3.2 before you export. If you export with it in place, the transparent background is filled with that color and the whole area prints as a solid block. This is the step most often missed, and the one most likely to scrap a whole batch.

1. Delete or hide the solid color layer, and every layer that should not print.
2. Confirm that every layer that should print is visible.
3. Confirm that the canvas background shows the grey-and-white checkerboard, which means it is transparent.
4. Confirm that the image size matches the target print size. See section 2.2.

4.2 Export the PNG

1. Click File → Export → Export As…
2. In the Export As window, set Format to PNG, and confirm that Transparency is selected.
   • Do not select “Smaller File (8-bit)”: the number of colors drops to 256, which can affect gradients and semi-transparent edges.
   • Do not select JPG: JPG has no transparency support, so the background is filled with white.
3. Click Export, choose the save location, enter a file name, then click Export again.
4. Save a PSD source file as well. It keeps the layers for later edits.

Note: If you print a CMYK comparison sample as described in section 2.4 and need to keep CMYK, save as TIFF, PSD, or PDF. Regular print delivery still uses a PNG with a transparent background.

4.2-1-Click-File-Export-Export-As

4.2-2-Set-Format-to-PNG-and-select-Transparency

4.2-3-Choose-the-save-location-and-export

4.3 After exporting

Open the exported PNG again and confirm:

• The background is transparent, shown as a grey-and-white checkerboard
• The design is complete and not cropped
• The size matches the target print size
• No new problem has appeared at the edges
• The solid color checking layer has not been exported by mistake

The PNG can now be imported into the RIP software for layout and printing.

After importing into the RIP software (PrintFactory), open the white ink channel preview. Confirm that the white ink outline aligns with the edges of the color design and does not spread beyond it. This finds leftover edge problems before printing, and saves film and time.

• White ink settings: Set White Ink Usage and Set White Undercoat Method
• Layout and size: Adjust Layout and Size
• Print profile: Select ICC Profile

5. Frequently asked questions

Q: Print quality is poor. Is the cause the image or the printer?

A: Do not conclude from “colors overall are not deep enough or look grey” that the image is at fault. Work through Troubleshoot Print Color Differences layer by layer. If only the areas meant to be pure black look grey, check Fix Dull or Grey Blacks. Banding across the print is an equipment-side problem, so contact technical support.

Q: How large can I print this image?

A: Use the pixel-to-size table in section 2.2. You can also check the size in Photoshop. Go to Image → Image Size. Clear the Resample checkbox and set Resolution to 300. The Width / Height values then show the suggested maximum print size at 300 PPI. Clearing Resample changes no pixels. It is a view-only step.

Q: Is a higher resolution always better? Does raising the value make the image sharper?

A: No. PPI is only the ratio between pixels and physical size. Raising the value on a low-pixel image adds no detail. It only makes the displayed size smaller. Sharpness comes from the total number of pixels, not from the PPI value.

Q: Does the image need to be converted to CMYK?

A: No conversion is needed. An RGB image can be printed directly. RGB and CMYK do print differently, but neither is better in every case. Judge by the printed result and by your own preference. If you convert, note that PNG does not keep CMYK; save as TIFF, PSD, or PDF instead.

Q: Black prints grey and not deep enough. What should I do?

A: Click the black area with the Eyedropper Tool and read the RGB values. If the area should be pure black but is not 0 / 0 / 0, correct it in the image. See Fix Dull or Grey Blacks. If it already reads 0 / 0 / 0, no further change to the image is needed. Troubleshoot Print Color Differences or contact technical support.

Q: Can I print a photo taken on a phone, or an image saved from a chat app?

A: This is not recommended. Chat apps compress images a second time during transfer, and most are JPG without a transparency channel. Ask for the original file or the design source file, then run every check in this document.

Q: Can I use an image downloaded from the internet?

A: Technically it has to pass every check in this document. Downloaded images commonly have too few pixels, a white JPG background, and compression artefacts already present at the edges. Confirm the copyright status of the design separately.

6. Related Documents

6.1 Image Preparation

This document is the entry point for this set. Continue based on the check result:

• Clean Image Edges — White edges, grey edges, unwanted semi-transparent edges, and leftover background.
• Fix Dull or Grey Blacks— Black areas that print grey or not dark enough.
• Troubleshoot Print Color Differences — Layer-by-layer troubleshooting for incorrect print colors.
• Why Print Colors Differ from Screen— Differences between the screen and the printed result.

6.2 RIP Software (PrintFactory) Settings

After exporting the PNG, continue with these RIP Software (PrintFactory) operations:

• RIP File Processing & Output Workflow— File processing and output workflow.
• Set White Ink Usage, Set White Undercoat Method, Set White Layer Choking
• Set Media Width (Print Area)— Set the printable width.
• Adjust Layout and Size— Size, copies, spacing, auto nesting, manual positioning and mirror printing.
• Manage Print ICC Profile, Select ICC Profile

LINKO Technical Support
Email: support@dtflinko.com
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