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Using dekapng to export a tiled version of an image
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| //////////////////////////////////////////////////////////////////////////////// | |
| // example of writing an RGBA png | |
| //////////////////////////////////////////////////////////////////////////////// | |
| // TODO: Define the contract that this expects the draw function to adhere to | |
| // - it should clear the screen if necessary | |
| // - it should render to completion | |
| // - it should be given a clean random state | |
| // | |
| // For this example, RenderContext contains a PicoGL App instance, which | |
| // contains a WebGL context. | |
| // | |
| // This function will call the provided "renderFn" repeatedly until all of the | |
| // tiles are rendered, and it will then return a blob that can be saved via | |
| // window.URL.createObjectURL(blob) | |
| // | |
| // renderContext: stores information about the current WebGL configuration/buffers, etc. | |
| // scale: the number of tiles to render in each direction | |
| // chunkSize: the width of each tile (this currently doesn't support other aspect ratios) | |
| // renderFn: a function that will be repeatedly called to render the scene. | |
| // Note: This function needs to reset the RNG state if that's used | |
| export function renderTiledExportBlob( | |
| renderContext: RenderContext, | |
| scale: number, | |
| chunkSize: number, | |
| renderFn: (context: RenderContext) => void | |
| ) { | |
| const pngRGBAWriter = new PNGRGBAWriter( | |
| chunkSize * scale, | |
| chunkSize * scale | |
| ) | |
| // iteration proceeds in rows | |
| for (let chunkY = scale - 1; chunkY >= 0; chunkY--) { | |
| // My coordinate system is from 0 to 1 on each axis | |
| // fit is a linear interpolation function that maps from one interval to another | |
| const yOffset = fit( | |
| chunkY, | |
| 0, | |
| scale - 1, | |
| 1.0 - 1.0 / scale, | |
| -1.0 + 1.0 / scale | |
| ) | |
| const rowChunks = [] | |
| for (let chunkX = 0; chunkX < scale; chunkX++) { | |
| console.log(`Rendering chunk [${chunkX}, ${chunkY}]`) | |
| const xOffset = fit( | |
| chunkX, | |
| 0, | |
| scale - 1, | |
| 1.0 - 1.0 / scale, | |
| -1.0 + 1.0 / scale | |
| ) | |
| // This tells WebGL to zoom into the current tile via scaling and translation | |
| setScaleAndOffset(renderContext, scale, xOffset, yOffset) | |
| renderFn(renderContext) | |
| const data = new Uint8Array(chunkSize * chunkSize * scale * 4) | |
| const gl = renderContext.app.gl | |
| gl.readPixels( | |
| 0, | |
| 0, | |
| chunkSize, | |
| chunkSize, | |
| gl.RGBA, | |
| gl.UNSIGNED_BYTE, | |
| data | |
| ) | |
| rowChunks.push(data) | |
| } | |
| for (let row = chunkSize - 1; row >= 0; --row) { | |
| rowChunks.forEach((chunk, _) => { | |
| const rowSize = chunkSize * 4 | |
| const chunkOffset = rowSize * row | |
| pngRGBAWriter.addPixels(chunk, chunkOffset, chunkSize) | |
| }) | |
| } | |
| } | |
| return pngRGBAWriter.finishAndGetBlob() | |
| } |
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