[壓縮PNG]有冇人睇得出壓咗有唔同?

bennetng

就咁 printscreen 佢網站, 然後將幅 printscreen 圖掟俾佢壓縮已經睇到有唔同

minazuki

Advanced lossy compression

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gamezz

回復 1 #chimp

右邊隻腳

via HKEPC Reader for Android

dvd-rw

FILE SIZE爭幾多先?

高登阿伯

回覆 1# chimp

網頁大大隻字Advanced lossy (有損)compression，壓咗當然唔同喇。

hihihi123hk

網上上傳圖片，再下載，其實唔關程式編寫事

有人話睇到壓咗有唔同，叫我唔好用。想求證。我的相好似header ...
chimp 發表於 2015-3-31 11:22

    識用一定係用呢隻 http://pngquant.org/ 既CLI  自己慢慢tune

Algorithm

pngquant uses modified version of Median Cut quantization algorithm and additional techniques to mitigate deficiencies of Median Cut.

Instead of splitting boxes with largest volume or number of colors, boxes are selected to minimize variance from their median value.

Histogram is built with addition of a basic perception model, which gives less weight to noisy areas of the image.

To improve color further, histogram is adjusted in a process similar to gradient descent (Median Cut is repeated many times with more weight on poorly represented colors).

Finally, colors are corrected using Voronoi iteration (K-means), which guarantees locally optimal palette.

pngquant works in premultiplied alpha color space to give less weight to transparent colors.

When remapping, error diffusion is applied only to areas where several neighboring pixels quantize to the same value, and which are not edges. This avoids adding noise to areas which have high visual quality without dithering.

henrywho

識用一定係用呢隻   既CLI  自己慢慢tune  
hihihi123hk 發表於 2015-4-1 01:58

ching 有冇使用心得?

gamezz

回覆 8# hihihi123hk

I am sure not much people have time to tuning the image file in real case.