Partitioning the PNG Reader for Integration — Handmade Hero — Episode Guide

0:00Recap and set the stage for the day working towards putting art into Handmade Hero

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0:00Recap and set the stage for the day working towards putting art into Handmade Hero

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0:00Recap and set the stage for the day working towards putting art into Handmade Hero

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3:08puremouron Is anyone else mesmerised by the bobbing orphan on the web page¹

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3:08puremouron Is anyone else mesmerised by the bobbing orphan on the web page¹

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3:08puremouron Is anyone else mesmerised by the bobbing orphan on the web page¹

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4:53Unpack the new art into a dedicated directory where the artist may dump art

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4:53Unpack the new art into a dedicated directory where the artist may dump art

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4:53Unpack the new art into a dedicated directory where the artist may dump art

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7:13Show off item_template.png and character_template.png

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7:13Show off item_template.png and character_template.png

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7:13Show off item_template.png and character_template.png

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9:20Discover how to switch the default image viewer back to the one that used to be the default

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9:20Discover how to switch the default image viewer back to the one that used to be the default

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9:20Discover how to switch the default image viewer back to the one that used to be the default

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13:08Switch the default image viewer back to Windows Photo viewer²

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13:08Switch the default image viewer back to Windows Photo viewer²

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13:08Switch the default image viewer back to Windows Photo viewer²

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14:28Show off our new art

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14:28Show off our new art

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14:28Show off our new art

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17:26Set up to read our new PNGs

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17:26Set up to read our new PNGs

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17:26Set up to read our new PNGs

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19:02Run our PNG reader on character_hero.png and crash in ConsumeSize()

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19:02Run our PNG reader on character_hero.png and crash in ConsumeSize()

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19:02Run our PNG reader on character_hero.png and crash in ConsumeSize()

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20:58Note in ParsePNG() the need to handle BTYPE0 blocks that straddle IDAT chunk boundaries

22:52Step through ParsePNG() to see that BFINAL does not get set

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22:52Step through ParsePNG() to see that BFINAL does not get set

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22:52Step through ParsePNG() to see that BFINAL does not get set

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28:28Let it run to completion, writing out our image

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28:28Let it run to completion, writing out our image

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28:28Let it run to completion, writing out our image

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28:55View character_hero.bmp to see that it looks correct but for the alpha channel

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28:55View character_hero.bmp to see that it looks correct but for the alpha channel

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28:55View character_hero.bmp to see that it looks correct but for the alpha channel

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31:10Inspect the Width and Height values, to see that they are as expected

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31:10Inspect the Width and Height values, to see that they are as expected

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31:10Inspect the Width and Height values, to see that they are as expected

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32:25Consult the DEFLATE,³ ZLIB⁴ and PNG⁵ specifications for information on BFINAL and chunk processing

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32:25Consult the DEFLATE,³ ZLIB⁴ and PNG⁵ specifications for information on BFINAL and chunk processing

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32:25Consult the DEFLATE,³ ZLIB⁴ and PNG⁵ specifications for information on BFINAL and chunk processing

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41:52Enable ParsePNG() to break out of its consumption loop once all the expected pixels have been consumed

43:19Run it successfully to see that the output looks correct

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43:19Run it successfully to see that the output looks correct

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43:19Run it successfully to see that the output looks correct

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43:52Run it successfully on hand_skeleton.png

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43:52Run it successfully on hand_skeleton.png

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43:52Run it successfully on hand_skeleton.png

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44:17Inspect the output image to see that it looks correct, and wonder if Photoshop's PNG encoder is busted

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44:17Inspect the output image to see that it looks correct, and wonder if Photoshop's PNG encoder is busted

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44:17Inspect the output image to see that it looks correct, and wonder if Photoshop's PNG encoder is busted

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46:55Remove stale code from WriteImageTopDownRGBA() and note in ParsePNG() to figure out why we can't rely on BFINAL being set to 1 on the last chunk of Photoshop-exported PNG files

49:47Consult stb_image.h for insight into its consumption loop

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49:47Consult stb_image.h for insight into its consumption loop

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49:47Consult stb_image.h for insight into its consumption loop

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53:51Set up to test our PNG image with stb_image.h

56:57Run stb_png_test successfully on character_hero.png

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56:57Run stb_png_test successfully on character_hero.png

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56:57Run stb_png_test successfully on character_hero.png

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1:00:37Step through stbi__parse_zlib() and into stbi__parse_uncompressed_block() to see that it processes 0-length blocks

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1:00:37Step through stbi__parse_zlib() and into stbi__parse_uncompressed_block() to see that it processes 0-length blocks

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1:00:37Step through stbi__parse_zlib() and into stbi__parse_uncompressed_block() to see that it processes 0-length blocks

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1:05:29Investigate the handling of 0-length blocks by FlushByte() in ParsePNG(), reverting the latter to break out of its consumption loop only if BFINAL is 1

1:07:24Set up to test our PNG reader on character_hero.png

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1:07:24Set up to test our PNG reader on character_hero.png

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1:07:24Set up to test our PNG reader on character_hero.png

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1:08:59Break on the FlushByte() call in ParsePNG() and realise that it may be flushing more than a byte

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1:08:59Break on the FlushByte() call in ParsePNG() and realise that it may be flushing more than a byte

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1:08:59Break on the FlushByte() call in ParsePNG() and realise that it may be flushing more than a byte

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1:10:02Change ParsePNG() to consume 16-bits for the LEN and NLEN, and FlushByte() to only flush the remainder of the byte

1:11:41Run it to see that we correctly parse character_hero.png

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1:11:41Run it to see that we correctly parse character_hero.png

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1:11:41Run it to see that we correctly parse character_hero.png

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1:12:19Enable ParsePNG() to parse blocks that straddle IDAT chunk boundaries, introducing RefillIfNecessary()

1:16:07Run it to see that it still works

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1:16:07Run it to see that it still works

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1:16:07Run it to see that it still works

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1:16:35Remove the ReversedBits table

1:17:19Determine to split up the PNG reader for integration into the game, while retaining the small test app

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1:17:19Determine to split up the PNG reader for integration into the game, while retaining the small test app

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1:17:19Determine to split up the PNG reader for integration into the game, while retaining the small test app

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1:18:23Create test_png.cpp to contain everything except the decoding code

1:22:07Consider supporting buffered error handling in the PNG decoder

1:24:01Create handmade_stream.cpp to contain all the stream consumption code for our PNG reader

1:32:03Introduce Outf() to write errors into our stream, augmenting the stream struct with Errors and stream_chunk with File and LineNumber

1:38:49Make test_png.cpp initialise an Info and Error stream, pass them to ReadEntireFile() and WriteImageTopDownRGBA(), and write those stream to file using a new DumpStreamToCRT()

1:44:16Introduce OnDemandMemoryStream()

1:45:02Compile and run and get no output, with a view to addressing that later

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1:45:02Compile and run and get no output, with a view to addressing that later

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1:45:02Compile and run and get no output, with a view to addressing that later

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1:45:16Q&A

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1:45:16Q&A

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1:45:16Q&A

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1:46:29ivereadthesequel Q: So what is the focus now? This logging / error system?

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1:46:29ivereadthesequel Q: So what is the focus now? This logging / error system?

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1:46:29ivereadthesequel Q: So what is the focus now? This logging / error system?

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1:48:18tonelessr Q: I haven't been following the PNG streams closely, but how satisfied are you with the code for the reader?

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1:48:18tonelessr Q: I haven't been following the PNG streams closely, but how satisfied are you with the code for the reader?

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1:48:18tonelessr Q: I haven't been following the PNG streams closely, but how satisfied are you with the code for the reader?

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1:49:13lvias Q: Could you explain the bug that was solved again?

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1:49:13lvias Q: Could you explain the bug that was solved again?

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1:49:13lvias Q: Could you explain the bug that was solved again?

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1:51:22flyinginthedark Q: Is TODO comment still in the code?

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1:51:22flyinginthedark Q: Is TODO comment still in the code?

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1:51:22flyinginthedark Q: Is TODO comment still in the code?

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1:51:57tonelessr Q: Any plans to switch to LLVM anytime in the series?

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1:51:57tonelessr Q: Any plans to switch to LLVM anytime in the series?

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1:51:57tonelessr Q: Any plans to switch to LLVM anytime in the series?

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1:52:41AsafGartner Q: If Visual Studio can load PNG files, maybe it can display BMP files with alpha?

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1:52:41AsafGartner Q: If Visual Studio can load PNG files, maybe it can display BMP files with alpha?

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1:52:41AsafGartner Q: If Visual Studio can load PNG files, maybe it can display BMP files with alpha?

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1:53:42Enable WriteImageTopDownRGBA() to conditionally replace the alpha pixels with all black, and the program to output this as an extra BMP file

1:58:38Run it and inspect our two output BMP files

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1:58:38Run it and inspect our two output BMP files

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1:58:38Run it and inspect our two output BMP files

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1:59:00Introduce MulAlpha() to composite the alpha and non-alpha pixels

2:03:06Run it to see our premultiplied output

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2:03:06Run it to see our premultiplied output

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2:03:06Run it to see our premultiplied output

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2:03:49tonelessr Q: This is off-topic, but will there be any blog posts on Molly Rocket for any of the projects anytime? Kind of miss those

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2:03:49tonelessr Q: This is off-topic, but will there be any blog posts on Molly Rocket for any of the projects anytime? Kind of miss those

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2:03:49tonelessr Q: This is off-topic, but will there be any blog posts on Molly Rocket for any of the projects anytime? Kind of miss those

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2:04:05cynokron Q: I am confused why you shift the multiply down by 8 bits. Wouldn't you want to mask with 0xFF?

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2:04:05cynokron Q: I am confused why you shift the multiply down by 8 bits. Wouldn't you want to mask with 0xFF?

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2:04:05cynokron Q: I am confused why you shift the multiply down by 8 bits. Wouldn't you want to mask with 0xFF?

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2:04:44Basis in Fixed Point Multiply

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2:04:44Basis in Fixed Point Multiply

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2:04:44Basis in Fixed Point Multiply

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2:11:05sneakybob_wot Q: Can you briefly explain how the binary reverse works you implemented last week?

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2:11:05sneakybob_wot Q: Can you briefly explain how the binary reverse works you implemented last week?

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2:11:05sneakybob_wot Q: Can you briefly explain how the binary reverse works you implemented last week?

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2:11:10Bit Reversal

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2:11:10Bit Reversal

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2:11:10Bit Reversal

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2:13:25We're all done

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2:13:25We're all done

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2:13:25We're all done

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