Hello. My application works extensively with png images. So Image based PNGReadWriter speed not enough for me. I have C library dll which has function "byte* readPNG(filename)". It returns buffer (pointer address) with same structure as Form Bitmap has. I use FFI to call this function. And I have very naive converter of returned buffer to Form: buffer := self primReadImageBytesFrom: imagePath. buffer getHandle asInteger == 0 ifTrue: [self error: 'bad image: ', imagePath ]. form := Form extent: width @ height depth: 32. x:= 0. y:=0. [y <= height ] whileTrue: [ x :=0. [x <= width] whileTrue: [ offset := x * 4 + (y * width * 4) + 1 + 8. value := buffer getHandle integerAt: offset size: 4 signed: false. form pixelValueAt: x@y put: value. x := x + 1. ]. y := y + 1. ]. ^form It's work and it is improve that buffer format similar to Form bits format. But such algorithm very slow. So my question is: How efficiently convert external byte array from FFI call to internal ByteArray (Bitmap, Form). I know about BitBlt class and blt := (BitBlt current toForm: f) sourceForm: source. blt combinationRule: Form over. "store" blt sourceX: 0; sourceY: 0; height: height; width: width. blt destX: 0; destY: 0. blt copyBits. And it works very fast. I try create source Form by source := Form extent: width@height depth: 32. source bits: buffer getHandle But BitBlt raise error for such form. #copyBits primitive failed and method execution continue with attempt to unhibernate given forms. Any ideas?