Fixed PdfColorspaceSpecialIndexed.ImageToRGB() (#259)

* Fixed PdfColorspaceSpecialIndexed.ImageToRGB() Fixes #258
* Fixed indexed colorspace bounds checking.
* Being super cautious to prevent a divide by zero error. I don't think the base cs can have <1 cpts.
* Updated image hash in extract_images_test.go to match new indexed colorspace code.
* add testfile from unipdf#258

internal/e2etest/extract_images_test.go

@@ -16,6 +16,8 @@ import (
 	"testing"
 
 	"github.com/stretchr/testify/require"
+	"github.com/stretchr/testify/assert"
+
 	"github.com/unidoc/unipdf/v3/common"
 	"github.com/unidoc/unipdf/v3/extractor"
 	"github.com/unidoc/unipdf/v3/model"
@@ -38,20 +40,21 @@ var knownExtrImgsHashes = map[string]string{
 	"7eee345c983461d44ae939b3f800a97642817c8d.pdf": "5a4cd00537f8a1f39fff2d4c6dd5cc53",
 	"52ab322c1697aca9bad37288f7c502e37fa657af.pdf": "2bddee02dff89a38c08322c9d2c779a6",
 	"0edf09fd438db2f18c1bb08fccc1f81a7b280bf2.pdf": "583f755b3fb1bd5697036616442687ab",
-	"cafe55316a45435c3817f4c1b6a19c9cd52db825.pdf": "b199badff0abb0311a2cbe35c7fce580",
+	"cafe55316a45435c3817f4c1b6a19c9cd52db825.pdf": "8b8c2eaa9b3a64eb5941348280c9c2a0",
 	"6773e6aa5d8a2d26362cf3fca2874b3a81025bae.pdf": "f052e3e333839508a8bdd8d1a3ba1973",
 	"d11a3ca55664828b69d7c39d83d5c0a63fcea89d.pdf": "29287cd44f009dce5aa9c2a0dc9a3c83",
 	"483933bf73cc4fcc264eb69214ff763ccf299e49.pdf": "627dcf88805786d03b2e76d367b42642",
 	"da1c5c4c4fe36f676dbca6ea01673c9fdf77c7a9.pdf": "7ffe076d1c7c88e07dfba7545b622ec6",
 	"f856baf7ffcd96003b6bda800171cb0e5680f78e.pdf": "a9505d8c22f1fd063fbe0b05aa33a5fc",
 	"201c20676fe8da14a8130852c91ed58b48cba8fb.pdf": "ffcb78d126c04be9ca2497bb43b6e964",
 	"f0152456494aa09e5cf82c4afe9ecd2fdc2e8d72.pdf": "d0e68157aaa7f9f4406807512db3e676",
-	"d95643acea1ec3f6215bda35e4cd89dbd8898c44.pdf": "1739aed3e1cbfa5e98f8d7fef17a614b",
+	"d95643acea1ec3f6215bda35e4cd89dbd8898c44.pdf": "b4c7c2ae9671af69f71e9965e9cf67e8",
 	"110d793aeaa7accbe40b5ab9db249d5a103d3b50.pdf": "a57e347edddfd3f6032b85553b3537cd",
 	"d15a0aa289524619a971188372dd05fb712f1b2c.pdf": "380907273bb8ea64943d986491d827ec",
 	"932e0dfa52c20ffe83b8178fb98296a0dab177d1.pdf": "b44d8b073f99ac3db28d7951e3c7d970",
 	"60a8c28da5c23081834adac4170755904d8c4166.pdf": "9167f381d5eed7a2e5fd10eca567c519",
 	"e51296be2615b9389482c9c16505286619b6cf36.pdf": "ec6e1f6297dd1cbda6ccba39e0c7d3d2",
+	"d3dd65300785dcf2114663397e475376bac88e75.pdf": "ea848ed888176368e697f577934f0452", // From unipdf#258.
 }
 
 func TestExtractImages(t *testing.T) {
@@ -93,7 +96,7 @@ func TestExtractImages(t *testing.T) {
 
 		knownHash, has := knownExtrImgsHashes[file.Name()]
 		if has {
-			require.Equal(t, knownHash, hash)
+			assert.Equal(t, knownHash, hash)
 			matchcount++
 		} else {
 			t.Logf("%s - hash: %s not in the list of known hashes", file.Name(), hash)

model/colorspace.go

@@ -2217,8 +2217,9 @@ func (cs *PdfColorspaceSpecialPattern) ImageToRGB(img Image) (Image, error) {
 	return img, errors.New("invalid colorspace for image (pattern)")
 }
 
-// PdfColorspaceSpecialIndexed is an indexed color space is a lookup table, where the input element is an index to the
-// lookup table and the output is a color defined in the lookup table in the Base colorspace.
+// PdfColorspaceSpecialIndexed is an indexed color space is a lookup table, where the input element
+// is an index to the lookup table and the output is a color defined in the lookup table in the Base
+// colorspace.
 // [/Indexed base hival lookup]
 type PdfColorspaceSpecialIndexed struct {
 	Base   PdfColorspace
@@ -2232,9 +2233,7 @@ type PdfColorspaceSpecialIndexed struct {
 
 // NewPdfColorspaceSpecialIndexed returns a new Indexed color.
 func NewPdfColorspaceSpecialIndexed() *PdfColorspaceSpecialIndexed {
-	cs := &PdfColorspaceSpecialIndexed{}
-	cs.HiVal = 255
-	return cs
+	return &PdfColorspaceSpecialIndexed{HiVal: 255}
 }
 
 func (cs *PdfColorspaceSpecialIndexed) String() string {
@@ -2401,32 +2400,38 @@ func (cs *PdfColorspaceSpecialIndexed) ImageToRGB(img Image) (Image, error) {
 	baseImage.Height = img.Height
 	baseImage.Width = img.Width
 	baseImage.alphaData = img.alphaData
-	baseImage.BitsPerComponent = img.BitsPerComponent
+	// TODO(peterwilliams97): Add support for other BitsPerComponent values.
+	// See https://github.com/unidoc/unipdf/issues/260
+	baseImage.BitsPerComponent = 8
 	baseImage.hasAlpha = img.hasAlpha
-	baseImage.ColorComponents = img.ColorComponents
+	baseImage.ColorComponents = cs.Base.GetNumComponents()
 
 	samples := img.GetSamples()
 	N := cs.Base.GetNumComponents()
 
+	if N < 1 {
+		return Image{}, fmt.Errorf("bad base colorspace NumComponents=%d", N)
+	}
+
 	var baseSamples []uint32
 	// Convert the indexed data to base color map data.
 	for i := 0; i < len(samples); i++ {
 		// Each data point represents an index location.
 		// For each entry there are N values.
-		index := int(samples[i]) * N
+		index := int(samples[i])
 		common.Log.Trace("Indexed: index=%d N=%d lut=%d", index, N, len(cs.colorLookup))
 		// Ensure does not go out of bounds.
-		if index+N-1 >= len(cs.colorLookup) {
+		if (index+1)*N > len(cs.colorLookup) {
 			// Clip to the end value.
-			index = len(cs.colorLookup) - N - 1
+			index = len(cs.colorLookup)/N - 1
 			common.Log.Trace("Clipping to index: %d", index)
 			if index < 0 {
 				common.Log.Debug("ERROR: Can't clip index. Is PDF file damaged?")
 				break
 			}
 		}
 
-		cvals := cs.colorLookup[index : index+N]
+		cvals := cs.colorLookup[index*N : (index+1)*N]
 		common.Log.Trace("C Vals: % d", cvals)
 		for _, val := range cvals {
 			baseSamples = append(baseSamples, uint32(val))