Batch Image Threshold Tool — Convert to Black and White
Batch process multiple images: convert to pure black and white by threshold. Processing takes place locally in your browser.
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What this tool actually does
The batch page accepts up to 30 browser-decodable images by multiple selection or drag and drop, with limits of 25 MiB and 24,000,000 decoded pixels per file and 100 MiB and 40,000,000 decoded pixels per batch.
Checkable behavior
Black-and-white threshold is the only effect setting, ranging from 0 to 255 and defaulting to 128. The same threshold is applied to all loaded files when Generate image is pressed.
Controls, output and limitations
Luminance is calculated with integer-weighted RGB coefficients (299R + 587G + 114B) / 1000. Pixels whose luminance is greater than or equal to the threshold become white; lower values become black. Alpha is retained.
At threshold 128, neutral RGB(128,128,128) has luminance 128 and becomes white, while RGB(127,127,127) becomes black. The output has only black or white RGB values and does not use dithering or adaptive/local thresholds.
Results preserve source dimensions and download separately as PNG files ending in -threshold.png. No ZIP, OCR, vector tracing, metadata retention or animation preservation is provided; processing stays in the browser.
Review every preview, then click Download all. It starts separate PNG downloads about 180 ms apart; there is no ZIP or per-image download button.
Per image: ≤25 MiB and ≤24,000,000 pixels. Per batch: ≤100 MiB and ≤40,000,000 pixels. Selecting over 30 files or any invalid image rejects the whole batch.
The threshold accepts finite decimal values from 0 to 255, including fractions such as 128.5. Blank, non-finite or out-of-range input is rejected; the previous preview and download are cleared.
Changing the threshold cancels a running batch, clears previous previews and disables downloads of the old results. Click Generate image again to process the batch with one fixed threshold. Clear also cancels the task and removes the input images.
Processing takes place locally in your browser.