How to Split a Transparent PNG Without Losing Transparency
Choose PNG as the output format before splitting. In CutMyImage, a transparent PNG is drawn onto a fresh canvas for each piece. PNG output keeps transparency; JPG output deliberately places the image over white. Changing the number of rows or columns does not turn transparency off. If an exported piece looks white, check its file format and view it over a dark background before assuming the alpha channel is gone.
Split the image in five steps
- Open the image splitter and upload your original PNG. Use the source file, rather than a screenshot of it on a white page.
- Choose columns, rows, or a grid. For a simple check, select a grid with 2 rows and 2 columns.
- Set Output format to PNG. This choice controls the downloaded pieces, regardless of the input filename.
- Press Split images. If you change the output format afterward, press the button again to rebuild the pieces; the previous downloads do not change themselves.
- Download the pieces individually or in a ZIP. Place a piece over both white and dark backgrounds. An actually transparent area reveals the background underneath.
The preview background is not part of the exported pixels. A checkerboard, white panel, or dark panel is a display aid. A checkerboard already painted into the input image, however, is ordinary image content and will remain in the pieces.
A four-quadrant transparency fixture you can reproduce
This page creates a 240 × 160 PNG with four flat-color quadrants. Each quadrant is 120 × 80, so a 2 × 2 split has exactly four pieces of 9,600 pixels. The regions use four different alpha values: 128, 64, 0, and 255. You can therefore distinguish partial transparency, complete transparency, and opaque color in one small source image.
The fixture is generated in your browser from the values below. It is not a screenshot, competitor image, or report of another tool's output. The table gives the expected PNG behavior for these exact inputs; it is a check you can run, rather than a claim that every browser and every downstream editor has been measured.
| Tile | Source region | Source RGBA | Expected alpha in PNG |
|---|---|---|---|
| Top left | x 0–119, y 0–79 | 255, 0, 0, 128 | 128: partly transparent red |
| Top right | x 120–239, y 0–79 | 0, 255, 0, 64 | 64: more transparent green |
| Bottom left | x 0–119, y 80–159 | 0, 0, 255, 0 | 0: completely transparent |
| Bottom right | x 120–239, y 80–159 | 0, 64, 128, 255 | 255: opaque blue |
The ranges are inclusive. Sample the center of each exported tile at local coordinate (60, 40), away from its edges. The matching source coordinates are (60, 40), (180, 40), (60, 120), and (180, 120). If your editor provides a pixel inspector, check alpha there. A fully transparent pixel's hidden RGB values are not a reliable preservation test: canvas processing can change invisible color data while retaining the same transparent appearance.
What to expect from the blank piece: the bottom-left PNG is still a 120 × 80 image. Its lack of visible color does not make it an empty file or a failed download. It contains a completely transparent region by design.
Why JPG pieces have a white background
CutMyImage's JPG path fills each piece's canvas with white before drawing the source. Its PNG path does not add that white fill. Consequently, choosing JPG converts partially transparent colors into colors blended against white and makes fully transparent areas white.
For an 8-bit alpha value A, an ideal white-background blend is C = (A / 255) × foreground + (1 − A / 255) × 255 for each red, green, and blue channel. This arithmetic describes the intended composite before JPEG compression; decoded JPEG colors can differ because compression is lossy and rendering may round values.
| Fixture region | Ideal color over white | Meaning |
|---|---|---|
| Red, alpha 128 | RGB 255, 127, 127 | The red becomes a pale red |
| Green, alpha 64 | RGB 191, 255, 191 | The green becomes a pale green |
| Blue, alpha 0 | RGB 255, 255, 255 | The transparent region becomes white |
| Blue, alpha 255 | RGB 0, 64, 128 | The opaque region stays opaque |
A higher JPG quality setting can reduce compression artifacts. It cannot bring back an alpha channel that was removed by this conversion. Returning to PNG also cannot infer the original transparent areas from a flattened JPG: start again from the original transparent source.
Choose a format for the pieces, not just for the source
- PNG: the simplest choice for this transparency check. It supports alpha and avoids JPEG-style lossy color compression. You still need a genuinely transparent source.
- JPG: use it when you want the pieces flattened on white. The splitter's white fill is intentional, so it is the wrong output choice for an overlay or transparent sprite.
- WebP: the format supports transparency. CutMyImage also offers WebP output through the browser's canvas exporter. Check the downloaded file and its alpha in your intended editor; the quality control is not a promise of lossless color encoding.
These format capabilities are documented in the PNG specification and Google's WebP documentation. The white-fill behavior and splitting instructions above describe CutMyImage's own implementation.
Questions about transparent image splitting
Why do the pieces look white in my file viewer?
The viewer may display transparent areas over white. Put the piece over a dark layer or use an editor's transparency grid. If both backgrounds show through, alpha is present. If the piece was exported as JPG, the white background is actually part of the converted image.
Will downloading a ZIP remove transparency?
A ZIP packages the exported files. It does not change a PNG into a JPG or flatten its pixels. Extract a piece and check that its extension and actual file type match the output format you chose.
Can I split a logo with a soft transparent edge?
Use the original PNG and PNG output. Inspect the edge over light and dark backgrounds. A pale fringe visible on both may already be baked into the source; a split does not automatically clean old background colors from partially transparent pixels.
Is the completely transparent tile an error?
Not in this fixture. The bottom-left region intentionally has alpha 0 everywhere. Its dimensions still count toward the original 240 × 160 image, and it should look empty over any background.
Does splitting preserve the original PNG file bytes?
No. Pieces are newly encoded image files, with new dimensions and containers. This guide checks visible transparency and selected alpha values. It does not promise identical metadata, compressed bytes, color-profile handling, or hidden RGB values.