Maxluli/SharpPngDecode
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Fixed the bug where the IDHD header would return mystic data and added full decoding of it. Also added the checks to prevent unrecognized code

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This commit is contained in:
Rohmer Maxime
2022-09-18 14:58:35 +02:00
parent e6c1329f2d
commit 4c0a2bc3d2
1 changed files with 48 additions and 7 deletions
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55
TEST_DecodePng/PngDecoder.cs
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@@ -74,7 +74,7 @@ namespace TEST_DecodePng
//As it is the first chunck, his structure is a little bit different
int imageWidth, imageHeight, bitDepth, colorType, compressionMethod, filterMethod, interfaceMethod;
int imageWidth, imageHeight, bitDepth, colorType, compressionMethod, filterMethod, interlaceMethod;
byte[] btaImageWidth = new byte[IMAGE_WIDTH_FIELD_SIZE];
byte[] btaImageHeight = new byte[IMAGE_HEIGHT_FIELD_SIZE];
@@ -92,10 +92,13 @@ namespace TEST_DecodePng
//Those are in little endien notation so we need to reverse it
Array.Reverse(btaImageWidth);
Array.Reverse(btaImageHeight);
imageWidth = BitConverter.ToInt32(btaImageWidth,0);
imageHeight = BitConverter.ToInt32(btaImageHeight,0);
imageWidth = BitConverter.ToInt32(btaImageWidth, 0);
imageHeight = BitConverter.ToInt32(btaImageHeight, 0);
//As specified in the documentation, images with 0 widht or height are invalid
if (imageWidth == 0 || imageHeight == 0)
return null;
cursor++;
bitDepth = Convert.ToInt32(content[cursor]);
cursor++;
colorType = Convert.ToInt32(content[cursor]);
@@ -104,7 +107,46 @@ namespace TEST_DecodePng
cursor++;
filterMethod = Convert.ToInt32(content[cursor]);
cursor++;
interfaceMethod = Convert.ToInt32(content[cursor]);
interlaceMethod = Convert.ToInt32(content[cursor]);
//Those are all the rules seen on the documentation at : https://www.w3.org/TR/PNG-Chunks.html
if (compressionMethod != 0 || filterMethod != 0 || interlaceMethod != 0 && interlaceMethod != 1)
return null;
switch (colorType)
{
case 0:
//Each pixel is a grayscale sample.
if (bitDepth != 1 && bitDepth != 2 && bitDepth != 4 && bitDepth != 8 && bitDepth != 16)
return null;
break;
case 2:
//Each pixel is an R,G,B triple.
if (bitDepth != 8 && bitDepth != 16)
return null;
break;
case 3:
//Each pixel is a palette index, a PLTE chunk must appear.
if (bitDepth != 1 && bitDepth != 2 && bitDepth != 4 && bitDepth != 8)
return null;
break;
case 4:
//Each pixel is a grayscale sample, followed by an alpha sample.
if (bitDepth != 8 && bitDepth != 16)
return null;
break;
case 6:
//Each pixel is an R,G,B triple, followed by an alpha sample.
if (bitDepth != 8 && bitDepth != 16)
return null;
break;
default:
//Only 0,2,3,4 and 6 are valid color type values
return null;
break;
}
MessageBox.Show("Image width: " + imageWidth +
Environment.NewLine + "Image height: " + imageHeight +
@@ -112,11 +154,10 @@ namespace TEST_DecodePng
Environment.NewLine + "color type : " + colorType +
Environment.NewLine + "compression method : " + compressionMethod +
Environment.NewLine + "filter method : " + filterMethod +
Environment.NewLine + "interface method : " + interfaceMethod
Environment.NewLine + "interface method : " + interlaceMethod
);
//Timing Stuff
chrono.Stop();
//Timing Stuff