Converting PNG Images to Other Formats

Under normal circumstances, converting PNG to JPEG may result in significant data loss, leading to color distortion or a decline in image quality. However, pixelUlti's compression feature ensures high-density compression while fully preserving the original colors of the image. After compression, we convert the image into three common formats, providing users with more options.

When converting PNG to JPEG, loss of quality occurs primarily because JPEG is a lossy compression format, whereas PNG is lossless. Here are the main reasons for the degradation:

1. Lossy Compression Causes Data Loss

PNG uses lossless compression, preserving all pixel data, while JPEG applies lossy compression through Discrete Cosine Transform (DCT) and quantization, which discard high-frequency details to achieve a smaller file size.

Since this quantization process is irreversible, once a PNG is converted to JPEG, some details are permanently lost.

2. Color Precision Reduction

PNG supports 24-bit RGB and 32-bit RGBA (with transparency), whereas JPEG only supports 24-bit RGB and uses the YCbCr color space, which compresses brightness (Y) and color components (Cb, Cr) differently.

Because the human eye is less sensitive to color variations, JPEG reduces chroma resolution (e.g., using 4:2:0 chroma subsampling), which can cause color distortions and loss of smooth color transitions.

3. Blurred Edges & Detail Loss

JPEG's DCT compression weakens high-frequency details, making sharp edges, text, and fine patterns appear blurry or pixelated.

This effect is especially noticeable in gradient colors, pure-color backgrounds, illustrations, and pixel-art images, where compression may cause color banding.

4. Transparency Loss

PNG supports alpha transparency, but JPEG does not. When converting a transparent PNG to JPEG, the transparent areas will be filled with a solid color (typically white or black), which may ruin the intended visual appearance.

5. Recompression Artifacts

If a PNG was originally converted from a high-quality JPEG, converting it back to JPEG introduces double compression, leading to even more loss of detail and increased artifacts.

The compression level in JPEG (e.g., quality settings of 90, 80, 70) determines how much detail is lost—the lower the setting, the more degradation occurs.

PixelUlti utilizes proprietary technology for image compression, with the biggest challenge occurring during PNG to JPEG conversion. We’ve made every effort to restore the image to its fullest, particularly in handling red and yellow pixels.