Opaque mining progress overlay with Sphax texture pack (should be transparent)

[deathcap]

Using http://bdcraft.net 64x, the breaking animation background is solid gray instead of transparent.

Not all texture packs have this problem (ok with ProgrammerArt v2, Faithful32, MC175)

[deathcap]

The color is 0x7f7f7f; suppose I could replace this color with 100% transparent alpha..

[deathcap]

Curious why the texture interpreted as transparent in MC, but not here. Non-zero alpha channel? Some kind of quirk with png color palettes? Faithful32 recently had a problem with transparency, pngout changed transparent to black (at least in MC, with certain mods), for unknown reasons: https://github.com/smenes/Faithful32/commit/f17bac011ab902743789ac3d71f4f14a73bcdf69#commitcomment-6163720

[deathcap]

Some discussion of transparency in MC texture packs at http://www.quora.com/How-does-transparency-work-in-Minecraft-texture-packs

destroy_stage_0.png's background does look like 0x7f7f7f opaque. But if this is replaced with transparent, then will textures not be able to use 0x7f7f7f grayscale?