Merge pull request #891 from blikblum/fix-grayscale-png

Fix transparent grayscale png

lib/image/png.js

@@ -49,10 +49,10 @@ class PNGImage {
 
     // For PNG color types 0, 2 and 3, the transparency data is stored in
     // a dedicated PNG chunk.
-    if (this.image.transparency.grayscale) {
+    if (this.image.transparency.grayscale != null) {
       // Use Color Key Masking (spec section 4.8.5)
       // An array with N elements, where N is two times the number of color components.
-      const val = this.image.transparency.greyscale;
+      const val = this.image.transparency.grayscale;
       return this.obj.data['Mask'] = [val, val];
 
     } else if (this.image.transparency.rgb) {
@@ -109,7 +109,8 @@ class PNGImage {
   splitAlphaChannel() {
     return this.image.decodePixels(pixels => {
       let a, p;
-      const colorByteSize = (this.image.colors * this.image.bits) / 8;
+      const colorCount = this.image.colors;
+      const colorByteSize = (colorCount * this.image.bits) / 8;
       const pixelCount = this.width * this.height;
       const imgData = new Buffer(pixelCount * colorByteSize);
       const alphaChannel = new Buffer(pixelCount);
@@ -117,9 +118,9 @@ class PNGImage {
       let i = p = a = 0;
       const len = pixels.length;
       while (i < len) {
-        imgData[p++] = pixels[i++];
-        imgData[p++] = pixels[i++];
-        imgData[p++] = pixels[i++];
+        for (let colorIndex = 0; colorIndex < colorCount; colorIndex++) {
+          imgData[p++] = pixels[i++];
+        }
         alphaChannel[a++] = pixels[i++];
       }
 

tests/unit/png.spec.js

@@ -10,7 +10,7 @@ describe("PNGImage", () => {
     const img = new PNGImage(fs.readFileSync(fileName), "I1");
     // noop data manipulation methods
     img.loadIndexedAlphaChannel = () => {
-      if (img.image.hasAlphaChannel) {
+      if (img.image.transparency.indexed) {
         img.alphaChannel = {};
       }
     };
@@ -59,6 +59,38 @@ describe("PNGImage", () => {
     });
   });
 
+  test("RGB white transparent", () => {
+    // ImageWidth = 32
+    // ImageHeight = 32
+    // BitDepth = 16
+    // ColorType = 2
+    // Compression = 0
+    // Filter = 0
+    // Interlace = 0
+
+    const img = createImage("./tests/images/pngsuite-rgb-transparent-white.png");
+
+    expect(img.obj.data).toMatchObject({
+      BitsPerComponent: 16,
+      ColorSpace: "DeviceRGB",
+      Filter: "FlateDecode",
+      Height: 32,
+      Length: 1932,
+      Subtype: "Image",
+      Type: "XObject",
+      Width: 32,
+      Mask: [255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255],
+      DecodeParms: expect.any(PDFReference)
+    });
+
+    expect(img.obj.data.DecodeParms.data).toMatchObject({
+      BitsPerComponent: 16,
+      Colors: 3,
+      Columns: 32,
+      Predictor: 15
+    });
+  });  
+
   test("RGB with Alpha", () => {
     // ImageWidth = 409
     // ImageHeight = 400
@@ -129,6 +161,141 @@ describe("PNGImage", () => {
     });
   });
 
+  test("Pallete indexed transparency", () => {
+    // ImageWidth = 32
+    // ImageHeight = 32
+    // BitDepth = 8
+    // ColorType = 3
+    // Compression = 0
+    // Filter = 0
+    // Interlace = 0
+
+    const img = createImage("./tests/images/pngsuite-palette-transparent-white.png");
+
+    expect(img.obj.data).toMatchObject({
+      BitsPerComponent: 8,
+      ColorSpace: ["Indexed", "DeviceRGB", 244, expect.any(PDFReference)],
+      Filter: "FlateDecode",
+      Height: 32,
+      Length: 650,
+      Subtype: "Image",
+      Type: "XObject",
+      Width: 32,
+      DecodeParms: expect.any(PDFReference),
+      SMask: expect.any(PDFReference),
+    });
+
+    expect(img.obj.data.DecodeParms.data).toMatchObject({
+      BitsPerComponent: 8,
+      Colors: 1,
+      Columns: 32,
+      Predictor: 15
+    });
+
+    expect(img.obj.data.SMask.data).toMatchObject({
+      BitsPerComponent: 8,
+      ColorSpace: "DeviceGray",
+      Decode: [
+        0,
+        1
+      ],
+      Filter: "FlateDecode",
+      Height: 32,
+      Length: 16,
+      Subtype: "Image",
+      Type: "XObject",
+      Width: 32,
+    });    
+  });
+
+  test("Grayscale", () => {
+    // ImageWidth = 428
+    // ImageHeight = 320
+    // BitDepth = 8
+    // ColorType = 0
+    // Compression = 0
+    // Filter = 0
+    // Interlace = 0
+
+    const img = createImage("./tests/images/glassware-noisy.png");
+
+    expect(img.obj.data).toMatchObject({
+      BitsPerComponent: 8,
+      ColorSpace: "DeviceGray",
+      Filter: "FlateDecode",
+      Height: 428,
+      Length: 82633,
+      Subtype: "Image",
+      Type: "XObject",
+      Width: 320,
+      DecodeParms: expect.any(PDFReference),  
+    });
+  });
+  
+  test("Grayscale black transparent", () => {
+    // ImageWidth = 32
+    // ImageHeight = 32
+    // BitDepth = 4
+    // ColorType = 0
+    // Compression = 0
+    // Filter = 0
+    // Interlace = 0
+
+    const img = createImage("./tests/images/pngsuite-gray-transparent-black.png");
+
+    expect(img.obj.data).toMatchObject({
+      BitsPerComponent: 4,
+      ColorSpace: "DeviceGray",
+      Filter: "FlateDecode",
+      Height: 32,
+      Length: 328,
+      Subtype: "Image",
+      Type: "XObject",
+      Width: 32,
+      Mask: [0, 0],
+      DecodeParms: expect.any(PDFReference),
+    });
+
+    expect(img.obj.data.DecodeParms.data).toMatchObject({
+      BitsPerComponent: 4,
+      Colors: 1,
+      Columns: 32,
+      Predictor: 15
+    });    
+  });
+
+  test("Grayscale white transparent", () => {
+    // ImageWidth = 32
+    // ImageHeight = 32
+    // BitDepth = 16
+    // ColorType = 0
+    // Compression = 0
+    // Filter = 0
+    // Interlace = 0
+
+    const img = createImage("./tests/images/pngsuite-gray-transparent-white.png");
+
+    expect(img.obj.data).toMatchObject({
+      BitsPerComponent: 16,
+      ColorSpace: "DeviceGray",
+      Filter: "FlateDecode",
+      Height: 32,
+      Length: 1212,
+      Subtype: "Image",
+      Type: "XObject",
+      Width: 32,
+      Mask: [255, 255],
+      DecodeParms: expect.any(PDFReference),
+    });
+
+    expect(img.obj.data.DecodeParms.data).toMatchObject({
+      BitsPerComponent: 16,
+      Colors: 1,
+      Columns: 32,
+      Predictor: 15
+    });
+  });  
+
   test("Grayscale with Alpha", () => {
     // ImageWidth = 112
     // ImageHeight = 112