fix wrong git ignore

internal/pdf/model/sampling/resample.go

@@ -0,0 +1,191 @@
+package sampling
+
+// Resample the raw data which is in 8-bit (byte) format as a different
+// bit count per sample, up to 32 bits (uint32).
+func ResampleBytes(data []byte, bitsPerSample int) []uint32 {
+	samples := []uint32{}
+
+	bitsLeftPerSample := bitsPerSample
+	var sample uint32
+	var remainder byte
+	remainderBits := 0
+
+	index := 0
+
+	i := 0
+	for i < len(data) {
+		// Start with the remainder.
+		if remainderBits > 0 {
+			take := remainderBits
+			if bitsLeftPerSample < take {
+				take = bitsLeftPerSample
+			}
+
+			sample = (sample << uint(take)) | uint32(remainder>>uint(8-take))
+			remainderBits -= take
+			if remainderBits > 0 {
+				remainder = remainder << uint(take)
+			} else {
+				remainder = 0
+			}
+			bitsLeftPerSample -= take
+			if bitsLeftPerSample == 0 {
+				//samples[index] = sample
+				samples = append(samples, sample)
+				bitsLeftPerSample = bitsPerSample
+				sample = 0
+				index++
+			}
+		} else {
+			// Take next byte
+			b := data[i]
+			i++
+
+			// 8 bits.
+			take := 8
+			if bitsLeftPerSample < take {
+				take = bitsLeftPerSample
+			}
+			remainderBits = 8 - take
+			sample = (sample << uint(take)) | uint32(b>>uint(remainderBits))
+
+			if take < 8 {
+				remainder = b << uint(take)
+			}
+
+			bitsLeftPerSample -= take
+			if bitsLeftPerSample == 0 {
+				//samples[index] = sample
+				samples = append(samples, sample)
+				bitsLeftPerSample = bitsPerSample
+				sample = 0
+				index++
+			}
+		}
+	}
+
+	// Take care of remaining samples (if enough data available).
+	for remainderBits >= bitsPerSample {
+		take := remainderBits
+		if bitsLeftPerSample < take {
+			take = bitsLeftPerSample
+		}
+
+		sample = (sample << uint(take)) | uint32(remainder>>uint(8-take))
+		remainderBits -= take
+		if remainderBits > 0 {
+			remainder = remainder << uint(take)
+		} else {
+			remainder = 0
+		}
+		bitsLeftPerSample -= take
+		if bitsLeftPerSample == 0 {
+			//samples[index] = sample
+			samples = append(samples, sample)
+			bitsLeftPerSample = bitsPerSample
+			sample = 0
+			index++
+		}
+	}
+
+	return samples
+}
+
+// Resample the raw data which is in <=32-bit (uint32) format as a different
+// bit count per sample, up to 32 bits (uint32).
+//
+// bitsPerOutputSample is the number of bits for each output sample (up to 32)
+// bitsPerInputSample is the number of bits used in each input sample (up to 32)
+func ResampleUint32(data []uint32, bitsPerInputSample int, bitsPerOutputSample int) []uint32 {
+	samples := []uint32{}
+
+	bitsLeftPerSample := bitsPerOutputSample
+	var sample uint32
+	var remainder uint32
+	remainderBits := 0
+
+	index := 0
+
+	i := 0
+	for i < len(data) {
+		// Start with the remainder.
+		if remainderBits > 0 {
+			take := remainderBits
+			if bitsLeftPerSample < take {
+				take = bitsLeftPerSample
+			}
+
+			sample = (sample << uint(take)) | uint32(remainder>>uint(bitsPerInputSample-take))
+			remainderBits -= take
+			if remainderBits > 0 {
+				remainder = remainder << uint(take)
+			} else {
+				remainder = 0
+			}
+			bitsLeftPerSample -= take
+			if bitsLeftPerSample == 0 {
+				//samples[index] = sample
+				samples = append(samples, sample)
+				bitsLeftPerSample = bitsPerOutputSample
+				sample = 0
+				index++
+			}
+		} else {
+			// Take next byte
+			b := data[i]
+			i++
+
+			// 32 bits.
+			take := bitsPerInputSample
+			if bitsLeftPerSample < take {
+				take = bitsLeftPerSample
+			}
+			remainderBits = bitsPerInputSample - take
+			sample = (sample << uint(take)) | uint32(b>>uint(remainderBits))
+
+			if take < bitsPerInputSample {
+				remainder = b << uint(take)
+			}
+
+			bitsLeftPerSample -= take
+			if bitsLeftPerSample == 0 {
+				//samples[index] = sample
+				samples = append(samples, sample)
+				bitsLeftPerSample = bitsPerOutputSample
+				sample = 0
+				index++
+			}
+		}
+	}
+
+	// Take care of remaining samples (if enough data available).
+	for remainderBits >= bitsPerOutputSample {
+		take := remainderBits
+		if bitsLeftPerSample < take {
+			take = bitsLeftPerSample
+		}
+
+		sample = (sample << uint(take)) | uint32(remainder>>uint(bitsPerInputSample-take))
+		remainderBits -= take
+		if remainderBits > 0 {
+			remainder = remainder << uint(take)
+		} else {
+			remainder = 0
+		}
+		bitsLeftPerSample -= take
+		if bitsLeftPerSample == 0 {
+			samples = append(samples, sample)
+			bitsLeftPerSample = bitsPerOutputSample
+			sample = 0
+			index++
+		}
+	}
+
+	// If there are partial output samples, pad with 0s.
+	if bitsLeftPerSample > 0 && bitsLeftPerSample < bitsPerOutputSample {
+		sample <<= uint(bitsLeftPerSample)
+		samples = append(samples, sample)
+	}
+
+	return samples
+}